Expanded docstring for _conv_value

Author: cbertinato

Diff for: pandas/io/excel.py

@@ -777,8 +777,18 @@ def _pop_header_name(row, index_col):
 
 def _conv_value(val):
     """ Convert numpy types to Python types for the Excel writers.
-        :obj:`datetime` and :obj:`date` formatting must be handled in the
-        writer. :obj:`str` representation is returned for all other types.
+
+        Parameters
+        ----------
+        val : object
+            Value to be written into cells
+
+        Returns
+        -------
+        If val is a numpy int, float, or bool, then the equivalent Python
+        types are returned. :obj:`datetime`, :obj:`date`, and :obj:`timedelta`
+        are passed and formatting must be handled in the writer. :obj:`str`
+        representation is returned for all other types.
     """
     if is_integer(val):
         val = int(val)