'Update fields w/ the lazily loaded definitions'

def _load_definition(self):

    if isinstance(self._definition, DefinitionLazyLoader):
        persisted_definition = self._definition.fetch()
        if (persisted_definition is not None):
            fields = self._definition.field_converter(persisted_definition.get('fields'))
            self._fields.update(fields)
            aside_fields_p = persisted_definition.get('aside_fields')
            if aside_fields_p:
                aside_fields = self._definition.field_converter(aside_fields_p)
                for (aside_type, fields) in aside_fields.iteritems():
                    self.aside_fields.setdefault(aside_type, {}).update(fields)
        self._definition = None
