code: def add_vcenter(self, **kwargs):
          
          config = ET.Element("config")
          vcenter = ET.SubElement(config, "vcenter",
                                  xmlns="urn:brocade.com:mgmt:brocade-vswitch")
          id = ET.SubElement(vcenter, "id")
          id.text = kwargs.pop('id')
          credentials = ET.SubElement(vcenter, "credentials")
          url = ET.SubElement(credentials, "url")
          url.text = kwargs.pop('url')
          username = ET.SubElement(credentials, "username")
          username.text = kwargs.pop('username')
          password = ET.SubElement(credentials, "password")
          password.text = kwargs.pop('password')
  
          try:
              self._callback(config)
              return True
  
          except Exception as error:
              logging.error(error)
              return False
docs: Add vCenter on the switch
  
          Args:
              id(str) : Name of an established vCenter
              url (bool) : vCenter URL
              username (str): Username of the vCenter
              password (str): Password of the vCenter
              callback (function): A function executed upon completion of the
                   method.
  
          Returns:
             Return value of `callback`.
  
          Raises:
              None