minor: doc

doc/api/gridfs/grid_file.rst

@@ -3,4 +3,8 @@
 
 .. automodule:: gridfs.grid_file
    :synopsis: Tools for representing files stored in GridFS
-   :members:
+
+   .. autoclass:: GridFile(file-spec, database[, mode='r'[, collection='fs']])
+      :members:
+
+      .. autoattribute:: _id

gridfs/grid_file.py

@@ -166,7 +166,9 @@ class GridFile(object):
 
     @property
     def _id(self):
-        """Get the value of ``"_id"`` for this :class:`GridFile`.
+        """The ``"_id"`` value for this :class:`GridFile`.
+
+        .. versionadded:: 1.5+
         """
         return self.__id