message: simplify structure of if ... return chain
diff: @@ -2038,13 +2038,10 @@ def get(identifier):
  """
  if identifier is None:
  return None
  - if isinstance(identifier, str):
  + if isinstance(identifier, str) or isinstance(identifier, dict):
  return deserialize(identifier)
  - if isinstance(identifier, dict):
  - return deserialize(identifier)
  - elif callable(identifier):
  + if callable(identifier):
  return identifier
  - else:
  raise ValueError(
  'Could not interpret loss function identifier: {}'.format(identifier))
  