message: add overwrite keyword
diff: @@ -57,16 +57,16 @@ class ParameterServer(Params):
  def __contains__(self, key):
  return key in self.store
  - def AppendParamServer(self, p_server):
  + def AppendParamServer(self, p_server, overwrite=False):
  for key in p_server.store.keys():
  if key in self.store:
  val_self = self.store[key]
  val_other = p_server.store[key]
  if isinstance(val_self, ParameterServer) and isinstance(val_other, ParameterServer):
  val_self.AppendParamServer(val_other)
  - else:
  + elif not overwrite:
  logging.warning("Cannot append conflicting key '{}'!".format(key))
  - else:
  + if not key in self.store or overwrite:
  self.__setitem__(key, p_server[key])
  def FindKey(self, param_key):
  