def fields_by_camelcase_name(self):
    """Same FieldDescriptor objects as in :attr:`fields`, but indexed by
    :attr:`FieldDescriptor.camelcase_name`.
    """
    if self._fields_by_camelcase_name is None:
      self._fields_by_camelcase_name = dict(
          (f.camelcase_name, f) for f in self.fields)
    return self._fields_by_camelcase_name
Same FieldDescriptor objects as in :attr:`fields`, but indexed by
    :attr:`FieldDescriptor.camelcase_name`.
    
deps/protobuf/python/google/protobuf/descriptor.py