@staticmethod<EOL><INDENT>def fill_extra_attributes(attributes):<DEDENT>
return attributes<EOL>
Implement in subclasses to fill extra attributes when an XML is transformed to an object.

        This is called just before initializing the entity.

        Args:
            attributes (dict) - Already transformed attributes that will be passed to entity create.

        Returns:
            Must return the attributes dictionary, possibly with changed or additional values.