code: def get_content_children(self, content_id, expand=None, parent_version=None, callback=None):
          
          params = {}
          if expand:
              params["expand"] = expand
          if parent_version:
              params["parentVersion"] = parent_version
          return self._service_get_request("rest/api/content/{id}/child".format(id=content_id), params=params,
                                           callback=callback)
docs: Returns a map of the direct children of a piece of Content. Content can have multiple types of children -
          for example a Page can have children that are also Pages, but it can also have Comments and Attachments.
  
          The {@link ContentType}(s) of the children returned is specified by the "expand" query parameter in the request
          - this parameter can include expands for multiple child types.
          If no types are included in the expand parameter, the map returned will just list the child types that
          are available to be expanded for the {@link Content} referenced by the "content_id" parameter.
          :param content_id (string): A string containing the id of the content to retrieve children for.
          :param expand (string): OPTIONAL :A comma separated list of properties to expand on the children.
                                  Default: None.
          :param parent_version (int): OPTIONAL: An integer representing the version of the content to retrieve
                                       children for. Default: 0 (Latest)
  
          :param callback: OPTIONAL: The callback to execute on the resulting data, before the method returns.
                           Default: None (no callback, raw data returned).
          :return: The JSON data returned from the content/{id}/child endpoint, or the results of the callback.
                   Will raise requests.HTTPError on bad input, potentially.