diff --git a/docker/Dockerfile.centos-7.9.2009 b/docker/Dockerfile.centos-7.9.2009
index a449688..b8a4ede 100644
--- a/docker/Dockerfile.centos-7.9.2009
+++ b/docker/Dockerfile.centos-7.9.2009
@@ -1,41 +1,41 @@
-FROM centos:7.9.2009 AS base
-
-# install base packages
-RUN yum -y install glibc-langpack-en glibc-langpack-ko python3 python3-pip
-RUN pip3 install --upgrade pip wheel
-
-# branch to build khaiii
-FROM base AS build
-RUN yum -y groupinstall "Development Tools" && \
-    yum -y install centos-release-scl && \
-    yum -y install devtoolset-7
-RUN pip3 install cmake
-COPY . /khaiii
-WORKDIR /khaiii/build
-RUN source /opt/rh/devtoolset-7/enable && \
-    cmake .. && \
-    make -j && \
-    make resource && \
-    test/khaiii && \
-    make install && \
-    make package_python
-WORKDIR /khaiii/build/package_python
-RUN source /opt/rh/devtoolset-7/enable && \
-    pip3 install .
-
-# branch to run khaiii
-FROM base AS runtime
-COPY --from=build /usr/local/bin/khaiii /usr/local/bin/
-COPY --from=build /usr/local/lib/libkhaiii.* /usr/local/lib/
-COPY --from=build /usr/local/share/khaiii/ /usr/local/share/khaiii/
-COPY --from=build /usr/local/include/khaiii/ /usr/local/include/khaiii/
-
-ENV PYTHON_VER=3.6
-ARG KHAIII_VER
-RUN echo "KHAIII_VER: ${KHAIII_VER}"
-RUN if [ "${KHAIII_VER}" = "" ]; then echo "build argument KHAIII_VER is not provided" && exit 1; fi
-COPY --from=build /usr/local/lib/python${PYTHON_VER}/site-packages/khaiii/ /usr/local/lib/python${PYTHON_VER}/site-packages/khaiii/
-COPY --from=build /usr/local/lib/python${PYTHON_VER}/site-packages/khaiii-${KHAIII_VER}.dist-info/ /usr/local/lib/python${PYTHON_VER}/site-packages/khaiii-${KHAIII_VER}.dist-info/
-
-ENV LANG=en_US.UTF-8
-WORKDIR /
+FROM centos:7.9.2009 AS base
+
+# install base packages
+RUN yum -y install glibc-langpack-en glibc-langpack-ko python3 python3-pip
+RUN pip3 install --upgrade pip wheel
+
+# branch to build khaiii
+FROM base AS build
+RUN yum -y groupinstall "Development Tools" && \
+    yum -y install centos-release-scl && \
+    yum -y install devtoolset-7
+RUN pip3 install cmake
+COPY . /khaiii
+WORKDIR /khaiii/build
+RUN source /opt/rh/devtoolset-7/enable && \
+    cmake .. && \
+    make -j && \
+    make resource && \
+    test/khaiii && \
+    make install && \
+    make package_python
+WORKDIR /khaiii/build/package_python
+RUN source /opt/rh/devtoolset-7/enable && \
+    pip3 install .
+
+# branch to run khaiii
+FROM base AS runtime
+COPY --from=build /usr/local/bin/khaiii /usr/local/bin/
+COPY --from=build /usr/local/lib/libkhaiii.* /usr/local/lib/
+COPY --from=build /usr/local/share/khaiii/ /usr/local/share/khaiii/
+COPY --from=build /usr/local/include/khaiii/ /usr/local/include/khaiii/
+
+ENV PYTHON_VER=3.6
+ARG KHAIII_VER
+RUN echo "KHAIII_VER: ${KHAIII_VER}"
+RUN if [ "${KHAIII_VER}" = "" ]; then echo "build argument KHAIII_VER is not provided" && exit 1; fi
+COPY --from=build /usr/local/lib/python${PYTHON_VER}/site-packages/khaiii/ /usr/local/lib/python${PYTHON_VER}/site-packages/khaiii/
+COPY --from=build /usr/local/lib/python${PYTHON_VER}/site-packages/khaiii-${KHAIII_VER}.dist-info/ /usr/local/lib/python${PYTHON_VER}/site-packages/khaiii-${KHAIII_VER}.dist-info/
+
+ENV LANG=en_US.UTF-8
+WORKDIR /
diff --git a/docker/Dockerfile.centos-8.3.2011 b/docker/Dockerfile.centos-8.3.2011
index 8b0b29a..52d98cc 100644
--- a/docker/Dockerfile.centos-8.3.2011
+++ b/docker/Dockerfile.centos-8.3.2011
@@ -1,37 +1,37 @@
-FROM centos:8.3.2011 AS base
-
-# install base packages
-RUN yum -y install glibc-langpack-en glibc-langpack-ko python3 python3-pip
-RUN pip3 install --upgrade pip wheel
-
-# branch to build khaiii
-FROM base AS build
-RUN yum -y groupinstall "Development Tools"
-RUN pip3 install cmake
-COPY . /khaiii
-WORKDIR /khaiii/build
-RUN cmake .. && \
-    make -j && \
-    make resource && \
-    test/khaiii && \
-    make install && \
-    make package_python
-WORKDIR /khaiii/build/package_python
-RUN pip3 install .
-
-# branch to run khaiii
-FROM base AS runtime
-COPY --from=build /usr/local/bin/khaiii /usr/local/bin/
-COPY --from=build /usr/local/lib/libkhaiii.* /usr/local/lib/
-COPY --from=build /usr/local/share/khaiii/ /usr/local/share/khaiii/
-COPY --from=build /usr/local/include/khaiii/ /usr/local/include/khaiii/
-
-ENV PYTHON_VER=3.6
-ARG KHAIII_VER
-RUN echo "KHAIII_VER: ${KHAIII_VER}"
-RUN if [ "${KHAIII_VER}" = "" ]; then echo "build argument KHAIII_VER is not provided" && exit 1; fi
-COPY --from=build /usr/local/lib/python${PYTHON_VER}/site-packages/khaiii/ /usr/local/lib/python${PYTHON_VER}/site-packages/khaiii/
-COPY --from=build /usr/local/lib/python${PYTHON_VER}/site-packages/khaiii-${KHAIII_VER}.dist-info/ /usr/local/lib/python${PYTHON_VER}/site-packages/khaiii-${KHAIII_VER}.dist-info/
-
-ENV LANG=ko_KR.UTF-8
-WORKDIR /
+FROM centos:8.3.2011 AS base
+
+# install base packages
+RUN yum -y install glibc-langpack-en glibc-langpack-ko python3 python3-pip
+RUN pip3 install --upgrade pip wheel
+
+# branch to build khaiii
+FROM base AS build
+RUN yum -y groupinstall "Development Tools"
+RUN pip3 install cmake
+COPY . /khaiii
+WORKDIR /khaiii/build
+RUN cmake .. && \
+    make -j && \
+    make resource && \
+    test/khaiii && \
+    make install && \
+    make package_python
+WORKDIR /khaiii/build/package_python
+RUN pip3 install .
+
+# branch to run khaiii
+FROM base AS runtime
+COPY --from=build /usr/local/bin/khaiii /usr/local/bin/
+COPY --from=build /usr/local/lib/libkhaiii.* /usr/local/lib/
+COPY --from=build /usr/local/share/khaiii/ /usr/local/share/khaiii/
+COPY --from=build /usr/local/include/khaiii/ /usr/local/include/khaiii/
+
+ENV PYTHON_VER=3.6
+ARG KHAIII_VER
+RUN echo "KHAIII_VER: ${KHAIII_VER}"
+RUN if [ "${KHAIII_VER}" = "" ]; then echo "build argument KHAIII_VER is not provided" && exit 1; fi
+COPY --from=build /usr/local/lib/python${PYTHON_VER}/site-packages/khaiii/ /usr/local/lib/python${PYTHON_VER}/site-packages/khaiii/
+COPY --from=build /usr/local/lib/python${PYTHON_VER}/site-packages/khaiii-${KHAIII_VER}.dist-info/ /usr/local/lib/python${PYTHON_VER}/site-packages/khaiii-${KHAIII_VER}.dist-info/
+
+ENV LANG=ko_KR.UTF-8
+WORKDIR /
diff --git a/docker/Dockerfile.pytorch b/docker/Dockerfile.pytorch
index 4cb7d3a..83a46c8 100644
--- a/docker/Dockerfile.pytorch
+++ b/docker/Dockerfile.pytorch
@@ -1,8 +1,8 @@
-FROM pytorch/pytorch:1.7.0-cuda11.0-cudnn8-runtime
-
-RUN pip install tensorboardX tqdm
-COPY . /khaiii
-WORKDIR /khaiii/train
-ENV PYTHONPATH=/khaiii/src/main/python
-RUN python split_corpus.py --input corpus/sample.txt --out-pfx corpus/sample --dev 4 --test 4
-RUN python train.py --in-pfx corpus/sample --batch-size 4
+FROM pytorch/pytorch:1.7.0-cuda11.0-cudnn8-runtime
+
+RUN pip install tensorboardX tqdm
+COPY . /khaiii
+WORKDIR /khaiii/train
+ENV PYTHONPATH=/khaiii/src/main/python
+RUN python split_corpus.py --input corpus/sample.txt --out-pfx corpus/sample --dev 4 --test 4
+RUN python train.py --in-pfx corpus/sample --batch-size 4
diff --git a/docker/Dockerfile.ubuntu b/docker/Dockerfile.ubuntu
index ea378c6..73e1334 100644
--- a/docker/Dockerfile.ubuntu
+++ b/docker/Dockerfile.ubuntu
@@ -1,52 +1,52 @@
-ARG UBUNTU_VER="18.04"
-FROM ubuntu:${UBUNTU_VER} AS base
-# supported ubuntu versions are 20.04, 18.04 and 16.04
-# you can build with passing --build-arg argument, such as "--build-arg UBUNTU_VER=20.04"
-
-# install base packages
-RUN apt -y update && \
-    apt -y install language-pack-ko python3 python3-pip
-RUN locale-gen en_US.UTF-8 && \
-    update-locale LANG=en_US.UTF-8
-RUN pip3 install --upgrade pip
-
-# branch to build khaiii
-FROM base AS build
-RUN apt -y install build-essential
-RUN pip3 install cmake
-COPY . /khaiii
-WORKDIR /khaiii/build
-RUN cmake .. && \
-    make -j && \
-    make resource && \
-    test/khaiii && \
-    make install && \
-    make package_python
-WORKDIR /khaiii/build/package_python
-RUN pip3 install .
-
-# branch to run khaiii
-FROM base AS runtime
-COPY --from=build /usr/local/bin/khaiii /usr/local/bin/
-COPY --from=build /usr/local/lib/libkhaiii.* /usr/local/lib/
-COPY --from=build /usr/local/share/khaiii/ /usr/local/share/khaiii/
-COPY --from=build /usr/local/include/khaiii/ /usr/local/include/khaiii/
-
-FROM runtime AS ubuntu-16.04
-ENV PYTHON_VER=3.5
-
-FROM runtime AS ubuntu-18.04
-ENV PYTHON_VER=3.6
-
-FROM runtime AS ubuntu-20.04
-ENV PYTHON_VER=3.8
-
-FROM ubuntu-${UBUNTU_VER}
-ARG KHAIII_VER
-RUN echo "KHAIII_VER: ${KHAIII_VER}"
-RUN if [ "${KHAIII_VER}" = "" ]; then echo "build argument KHAIII_VER is not provided" && exit 1; fi
-COPY --from=build /usr/local/lib/python${PYTHON_VER}/dist-packages/khaiii/ /usr/local/lib/python${PYTHON_VER}/dist-packages/khaiii/
-COPY --from=build /usr/local/lib/python${PYTHON_VER}/dist-packages/khaiii-${KHAIII_VER}.dist-info/ /usr/local/lib/python${PYTHON_VER}/dist-packages/khaiii-${KHAIII_VER}.dist-info/
-
-ENV LANG=ko_KR.UTF-8
-WORKDIR /
+ARG UBUNTU_VER="18.04"
+FROM ubuntu:${UBUNTU_VER} AS base
+# supported ubuntu versions are 20.04, 18.04 and 16.04
+# you can build with passing --build-arg argument, such as "--build-arg UBUNTU_VER=20.04"
+
+# install base packages
+RUN apt -y update && \
+    apt -y install language-pack-ko python3 python3-pip
+RUN locale-gen en_US.UTF-8 && \
+    update-locale LANG=en_US.UTF-8
+RUN pip3 install --upgrade pip
+
+# branch to build khaiii
+FROM base AS build
+RUN apt -y install build-essential
+RUN pip3 install cmake
+COPY . /khaiii
+WORKDIR /khaiii/build
+RUN cmake .. && \
+    make -j && \
+    make resource && \
+    test/khaiii && \
+    make install && \
+    make package_python
+WORKDIR /khaiii/build/package_python
+RUN pip3 install .
+
+# branch to run khaiii
+FROM base AS runtime
+COPY --from=build /usr/local/bin/khaiii /usr/local/bin/
+COPY --from=build /usr/local/lib/libkhaiii.* /usr/local/lib/
+COPY --from=build /usr/local/share/khaiii/ /usr/local/share/khaiii/
+COPY --from=build /usr/local/include/khaiii/ /usr/local/include/khaiii/
+
+FROM runtime AS ubuntu-16.04
+ENV PYTHON_VER=3.5
+
+FROM runtime AS ubuntu-18.04
+ENV PYTHON_VER=3.6
+
+FROM runtime AS ubuntu-20.04
+ENV PYTHON_VER=3.8
+
+FROM ubuntu-${UBUNTU_VER}
+ARG KHAIII_VER
+RUN echo "KHAIII_VER: ${KHAIII_VER}"
+RUN if [ "${KHAIII_VER}" = "" ]; then echo "build argument KHAIII_VER is not provided" && exit 1; fi
+COPY --from=build /usr/local/lib/python${PYTHON_VER}/dist-packages/khaiii/ /usr/local/lib/python${PYTHON_VER}/dist-packages/khaiii/
+COPY --from=build /usr/local/lib/python${PYTHON_VER}/dist-packages/khaiii-${KHAIII_VER}.dist-info/ /usr/local/lib/python${PYTHON_VER}/dist-packages/khaiii-${KHAIII_VER}.dist-info/
+
+ENV LANG=ko_KR.UTF-8
+WORKDIR /