code: def to_deprecated_son(self, prefix='', tag='i4x'):
          
          # 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
docs: Returns a SON object that represents this location