Remove the parent workitem from current workitem

        Notice: for a certain workitem, no more than one parent workitem
        can be added and specified

def removeParent(self):
        """Remove the parent workitem from current workitem

        Notice: for a certain workitem, no more than one parent workitem
        can be added and specified

        """

        self.log.debug("Try to remove the parent workitem from current "
                       "<Workitem %s>",
                       self)

        headers = copy.deepcopy(self.rtc_obj.headers)
        headers["Content-Type"] = self.OSLC_CR_JSON
        req_url = "".join([self.url,
                           "?oslc_cm.properties=com.ibm.team.workitem.",
                           "linktype.parentworkitem.parent"])

        parent_tag = ("rtc_cm:com.ibm.team.workitem.linktype."
                      "parentworkitem.parent")
        parent_original = {parent_tag: []}

        self.put(req_url,
                 verify=False,
                 proxies=self.rtc_obj.proxies,
                 headers=headers,
                 data=json.dumps(parent_original))
        self.log.info("Successfully remove the parent workitem of current "
                      "<Workitem %s>",
                      self)