code: def p_example(self, p):
          
          if len(p) > 4:
              seen_fields = set()
              for example_field in p[6]:
                  if example_field.name in seen_fields:
                      self.errors.append(
                          ("Example with label '%s' defines field '%s' more "
                          "than once." % (p[2], example_field.name),
                          p.lineno(1), self.path))
                  seen_fields.add(example_field.name)
              p[0] = AstExample(
                  self.path, p.lineno(1), p.lexpos(1), p[2], p[5],
                  OrderedDict((f.name, f) for f in p[6]))
          else:
              p[0] = AstExample(
                  self.path, p.lineno(1), p.lexpos(1), p[2], None, OrderedDict())
docs: example : KEYWORD ID NL INDENT docsection example_fields DEDENT
                     | KEYWORD ID NL