code: def check_output(self, make_ndx_output, message=None, err=None):
          
          if message is None:
              message = ""
          else:
              message = '\n' + message
          def format(output, w=60):
              hrule = "====[ GromacsError (diagnostic output) ]".ljust(w,"=")
              return hrule + '\n' + str(output) + hrule
  
          rc = True
          if self._is_empty_group(make_ndx_output):
              warnings.warn("Selection produced empty group.{message!s}".format(**vars()), category=GromacsValueWarning)
              rc = False
          if self._has_syntax_error(make_ndx_output):
              rc = False
              out_formatted = format(make_ndx_output)
              raise GromacsError("make_ndx encountered a Syntax Error, "
                                 "%(message)s\noutput:\n%(out_formatted)s" % vars())
          if make_ndx_output.strip() == "":
              rc = False
              out_formatted = format(err)
              raise GromacsError("make_ndx produced no output, "
                                 "%(message)s\nerror output:\n%(out_formatted)s" % vars())
          return rc
docs: Simple tests to flag problems with a ``make_ndx`` run.