a method to remove an active container
            
        :param container_alias: string with name or id of container 
        :return: string with container id

def rm(self, container_alias):

        '''
            a method to remove an active container
            
        :param container_alias: string with name or id of container 
        :return: string with container id
        '''

        title = '%s.rm' % self.__class__.__name__

    # validate inputs
        input_fields = {
            'container_alias': container_alias
        }
        for key, value in input_fields.items():
            object_title = '%s(%s=%s)' % (title, key, str(value))
            self.fields.validate(value, '.%s' % key, object_title)

    # run remove command
        sys_cmd = 'docker rm -f %s' % container_alias
        output_lines = self.command(sys_cmd).split('\n')

        return output_lines[0]