diff --git a/python/google/protobuf/message.py b/python/google/protobuf/message.py
index de2f569..eeb0d57 100755
--- a/python/google/protobuf/message.py
+++ b/python/google/protobuf/message.py
@@ -184,9 +184,15 @@
     self.Clear()
     self.MergeFromString(serialized)
 
-  def SerializeToString(self):
+  def SerializeToString(self, **kwargs):
     """Serializes the protocol message to a binary string.
 
+    Arguments:
+      **kwargs: Keyword arguments to the serialize method, accepts
+        the following keyword args:
+        deterministic: If true, requests deterministic serialization of the
+          protobuf, with predictable ordering of map keys.
+
     Returns:
       A binary string representation of the message if all of the required
       fields in the message are set (i.e. the message is initialized).
@@ -196,12 +202,18 @@
     """
     raise NotImplementedError
 
-  def SerializePartialToString(self):
+  def SerializePartialToString(self, **kwargs):
     """Serializes the protocol message to a binary string.
 
     This method is similar to SerializeToString but doesn't check if the
     message is initialized.
 
+    Arguments:
+      **kwargs: Keyword arguments to the serialize method, accepts
+        the following keyword args:
+        deterministic: If true, requests deterministic serialization of the
+          protobuf, with predictable ordering of map keys.
+
     Returns:
       A string representation of the partial message.
     """
@@ -225,10 +237,11 @@
   # """
   def ListFields(self):
     """Returns a list of (FieldDescriptor, value) tuples for all
-    fields in the message which are not empty.  A singular field is non-empty
-    if HasField() would return true, and a repeated field is non-empty if
-    it contains at least one element.  The fields are ordered by field
-    number"""
+    fields in the message which are not empty.  A message field is
+    non-empty if HasField() would return true. A singular primitive field
+    is non-empty if HasField() would return true in proto2 or it is non zero
+    in proto3. A repeated field is non-empty if it contains at least one
+    element.  The fields are ordered by field number"""
     raise NotImplementedError
 
   def HasField(self, field_name):
@@ -255,6 +268,9 @@
   def ClearExtension(self, extension_handle):
     raise NotImplementedError
 
+  def DiscardUnknownFields(self):
+    raise NotImplementedError
+
   def ByteSize(self):
     """Returns the serialized size of this message.
     Recursively calls ByteSize() on all contained messages.