Get vCenter hosts on the switch

        Args:

            callback (function): A function executed upon completion of the
                 method.

        Returns:
           Returns a list of vcenters

        Raises:
            None

def get_vcenter(self, **kwargs):
        """
        Get vCenter hosts on the switch

        Args:

            callback (function): A function executed upon completion of the
                 method.

        Returns:
           Returns a list of vcenters

        Raises:
            None
        """
        config = ET.Element("config")
        urn = "urn:brocade.com:mgmt:brocade-vswitch"
        ET.SubElement(config, "vcenter", xmlns=urn)
        output = self._callback(config, handler='get_config')
        result = []
        element = ET.fromstring(str(output))
        for vcenter in element.iter('{%s}vcenter'%urn):
            vc = {}
            vc['name'] = vcenter.find('{%s}id' % urn).text
            vc['url'] = (vcenter.find('{%s}credentials' % urn)).find('{%s}url' % urn).text
            isactive = vcenter.find('{%s}activate' %urn)
            if isactive is None:
                vc['isactive'] = False
            else:
                vc['isactive'] = True
            result.append(vc)
        return result