docs: def getChildren(self, returned_properties=None):
          """Get all the children workitems of this workitem
  
          If no children, None will be returned.
  
          :param returned_properties: the returned properties that you want.
              Refer to :class:`rtcclient.client.RTCClient` for more explanations
          :return: a :class:`rtcclient.workitem.Workitem` object
          :rtype: rtcclient.workitem.Workitem
          """
  
          children_tag = ("rtc_cm:com.ibm.team.workitem.linktype."
                          "parentworkitem.children")
          rp = returned_properties
          return (self.rtc_obj
                      ._get_paged_resources("Children",
                                            workitem_id=self.identifier,
                                            customized_attr=children_tag,
                                            page_size="10",
                                            returned_properties=rp))