code: def rest_instances(self, file_path=None, sort_keys=False):
          
          if not file_path:
              outputdir_path = BuiltIn().get_variable_value("${OUTPUTDIR}")
              if self.request["netloc"]:
                  file_path = (
                      path.join(outputdir_path, self.request["netloc"]) + ".json"
                  )
              else:
                  file_path = path.join(outputdir_path, "instances") + ".json"
          sort_keys = self._input_boolean(sort_keys)
          content = dumps(
              self.instances,
              ensure_ascii=False,
              indent=4,
              separators=(",", ": "),
              sort_keys=sort_keys,
          )
          try:
              with open(file_path, "w", encoding="utf-8") as file:
                  if IS_PYTHON_2:
                      content = unicode(content)
                  file.write(content)
          except IOError as e:
              raise RuntimeError(
                  "Error exporting instances "
                  + "to file '%s':\n%s" % (file_path, e)
              )
          return self.instances
docs: *Writes the instances as JSON to a file.*
  
          The instances are written to file as a JSON array of JSON objects,
          each object representing a single instance, and having three properties:
  
          - the request
          - the response
          - the schema for both, which have been updated according to the tests
  
          The file is created if it does not exist, otherwise it is truncated.
  
          *Options*
  
          ``sort_keys``: If true, the instances are sorted alphabetically by
          property names.
  
          *Examples*
  
          | `Rest Instances` | ${CURDIR}/log.json |