diff --git a/graph_def_editor/base_graph.py b/graph_def_editor/base_graph.py
index 4f295e5..f06b134 100644
--- a/graph_def_editor/base_graph.py
+++ b/graph_def_editor/base_graph.py
@@ -53,7 +53,9 @@ def __init__(
           name = None, # type: str
           ):
     """
-    Wrap a tf.GraphDef protocol buffer in a Graph object.
+    Constructor to be called by subclasses only.
+
+    Initializes attributes of this base class.
 
     Args:
       name: Optional human-readable name for the graph. If not provided,
@@ -137,6 +139,8 @@ def add_node(self,
       uniquify_name: Generate a unique name from this name if the graph
         already has a node with the indicated name. If False, raise an
         exception if the name is in use.
+      debug_info: Some internal TensorFlow debug information.
+        We just pass it through for safety.
 
     Returns:
       `MutableNode` wrapper for the new node.
@@ -265,6 +269,7 @@ def add_variable(self, name):
     v = variable.Variable(self)
     v.name = name
     self._variable_name_to_variable[name] = v
+    self.increment_version_counter()
     return v
 
   def add_variable_from_variable_def(self, variable_def,
diff --git a/graph_def_editor/function_graph.py b/graph_def_editor/function_graph.py
index afc0736..dc412d0 100644
--- a/graph_def_editor/function_graph.py
+++ b/graph_def_editor/function_graph.py
@@ -47,12 +47,7 @@
 
 
 class FunctionGraph(base_graph.BaseGraph):
-  """Wrapper class for TensorFlow function graphs.
-
-  Summary of internal data structures:
-  * _node_name_to_node: Nodes in the graph, stored as a dictionary. Key is name.
-  * _version: Counter that increments every time the graph is modified
-  """
+  """Wrapper class for TensorFlow function graphs."""
 
   def __init__(
       self,
@@ -78,7 +73,6 @@ def __init__(
           [(dtype, shape) for (dtype, shape, _) in tuples]
 
     # Populate fields of object
-    self._node_name_to_node = {}  # Dict[str, node.Node]; key is node name
     self._node_to_frame_names = None
     self._frame_name_to_nodes = None
     self._head_name_to_coloc_group = None  # Dict[str, FrozenList[str]]
diff --git a/graph_def_editor/graph.py b/graph_def_editor/graph.py
index 54d580d..bf2d004 100644
--- a/graph_def_editor/graph.py
+++ b/graph_def_editor/graph.py
@@ -311,10 +311,11 @@ def to_graph_def(self, add_shapes=True):
     for op in self.nodes:
       op.to_node_def(ret.node.add(), add_shapes)
 
-    # Pass through library without modifications for now.
+    # Copy library as is.
     if self._graph_def and self._graph_def.library:
       ret.library.CopyFrom(self._graph_def.library)
 
+    # Update functions in library that were instantiated as function graphs.
     for f_name, f_graph in self._function_graphs.items():
       function_index_to_update = None
       for index in range(0, len(ret.library.function)):
@@ -716,6 +717,9 @@ def breadth_first_visitor(
     """
     Visit all nodes reachable from a starting set in the order of a
     breadth-first traversal (going from node to output edges).
+    If visitor gets to a function call, and iterate_functions is True,
+    it will iterate all function nodes first and then continue with
+    remaining nodes in the graph.
     Invokes a callback at each node visited.
 
     Args:
@@ -731,7 +735,7 @@ def breadth_first_visitor(
           that we should also iterate through all function callers up
           the stack.
     Returns:
-      True if iteration was iterruputed by visitor, otherwise False.
+      True if iteration was interrupted by visitor, otherwise False.
     """
     if starting_nodes is None:
       # Start with all of the nodes in the graph that have no inputs.
@@ -818,6 +822,9 @@ def backwards_breadth_first_visitor(
     """
     Visit all nodes reachable from a starting set in the order of a
     backwards breadth-first traversal (going from node to input edges).
+    If visitor gets to a function call, and iterate_functions is True,
+    it will iterate all function nodes first and then continue with
+    remaining nodes in the graph.
     Invokes a callback at each node visited.
 
     Args:
@@ -830,7 +837,7 @@ def backwards_breadth_first_visitor(
           that we should also iterate through all function callers up
           the stack.
     Returns:
-      True if iteration was iterruputed by visitor, otherwise False.
+      True if iteration was interrupted by visitor, otherwise False.
     """
     if not starting_nodes:
       raise ValueError("starting_nodes is not provided")
diff --git a/graph_def_editor/node.py b/graph_def_editor/node.py
index bb312df..943e893 100644
--- a/graph_def_editor/node.py
+++ b/graph_def_editor/node.py
@@ -23,7 +23,7 @@
 if sys.version >= '3':
   from typing import Tuple, List, Iterable, Any, AbstractSet, Type
 
-from graph_def_editor import tensor, util
+from graph_def_editor import base_graph, tensor, util
 
 # Magical attribute name that TensorFlow uses to store colocation groups.
 # See colocation_groups property below for more information.
@@ -87,7 +87,7 @@ def __init__(self,
       device: TensorFlow device specification string indicating where this node
         should be located. Default value of "" means "use the default device"
     """
-    _type_check(g, graph.Graph, "g")
+    _type_check(g, base_graph.BaseGraph, "g")
     _type_check(node_id, int, "node_id")
     _type_check(name, str, "name")
     _type_check(op_name, str, "op_name")