Updates a security group

def update_security_group(self, sec_grp, name=None, desc=None):
        '''
        Updates a security group
        '''
        sec_grp_id = self._find_security_group_id(sec_grp)
        body = {'security_group': {}}
        if name:
            body['security_group']['name'] = name
        if desc:
            body['security_group']['description'] = desc
        return self.network_conn.update_security_group(sec_grp_id,
                                                       body=body)