'Renames the server
:param  server_id: ID of the server you want to rename
:param  name: New name of the server
:rtype: ``str``
:param description: New description of the server
:rtype: ``str``
:return:    Instance of class ``Node``
:rtype:     :class: `Node`'

def ex_rename_server(self, server_id, name=None, description=None):

    body = {}
    if (name is not None):
        body['name'] = name
    if (description is not None):
        body['description'] = description
    response = self.connection.request(action=('servers/%s' % server_id), data=body, method='PUT')
    return self._to_node(response.object)
