def to_deprecated_son(self, prefix='', tag='i4x'):
        """
        Returns a SON object that represents this location
        """
        # This preserves the old SON keys ('tag', 'org', 'course', 'category', 'name', 'revision'),
        # because that format was used to store data historically in mongo

        # adding tag b/c deprecated form used it
        son = SON({prefix + 'tag': tag})
        for field_name in ('org', 'course'):
            # Temporary filtering of run field because deprecated form left it out
            son[prefix + field_name] = getattr(self.course_key, field_name)
        for (dep_field_name, field_name) in [('category', 'block_type'), ('name', 'block_id')]:
            son[prefix + dep_field_name] = getattr(self, field_name)

        son[prefix + 'revision'] = self.course_key.branch
        return son
Returns a SON object that represents this location