def change_password(self, usrname, oldpwd, newpwd, callback=None):
        '''
        Change password.
        '''
        params = {'usrName': usrname,
                  'oldPwd' : oldpwd,
                  'newPwd' : newpwd,
                 }
        return self.execute_command('changePassword',
                                    params, callback=callback)
Change password.