docs: def command(self, sys_command):
  
          '''
              a method to run a system command in a separate shell
  
          :param sys_command: string with docker command
          :return: string output from docker
          '''
  
          title = '%s.command' % self.__class__.__name__
  
      # validate inputs
          input_fields = {
              'sys_command': sys_command
          }
          for key, value in input_fields.items():
              object_title = '%s(%s=%s)' % (title, key, str(value))
              self.fields.validate(value, '.%s' % key, object_title)
  
          from subprocess import check_output, STDOUT, CalledProcessError
          try:
              output = check_output(sys_command, shell=True, stderr=STDOUT).decode('utf-8')
          except CalledProcessError as err:
              raise Exception(err.output.decode('ascii', 'ignore'))
  
          return output