Raise ValueError on deg with not enough columns.

Fixes #37

mdtk/degradations.py

@@ -104,8 +104,18 @@ def pre_process(df, sort=False):
     -------
     df : pd.DataFrame
         The postprocessed dataframe.
+
+    Raises
+    ------
+    ValueError
+        If the given df does not have all of the necessary columns.
     """
-    df = df.loc[:, NOTE_DF_SORT_ORDER]
+    try:
+        df = df.loc[:, NOTE_DF_SORT_ORDER]
+    except KeyError:  # df has incorrect columns
+        raise ValueError(
+            f"Input note_df must have all of the columns: {NOTE_DF_SORT_ORDER}"
+        )
     if sort:
         df = df.sort_values(NOTE_DF_SORT_ORDER)
     df = df.reset_index(drop=True)

mdtk/tests/test_degradations.py

@@ -90,6 +90,11 @@ def test_pre_process():
         f"instead of \n{float_res}"
     )
 
+    # Check not correct columns raises ValueError
+    invalid_df = pd.DataFrame({"track": [0, 1], "onset": [0, 50], "pitch": [10, 20]})
+    with pytest.raises(ValueError):
+        deg.pre_process(invalid_df)
+
 
 def test_post_process():
     basic_res = pd.DataFrame(