code: def open_gsr(self):
          
          gsr_path = self.gsr_path
          if not gsr_path:
              if self.status == self.S_OK:
                  logger.critical("%s reached S_OK but didn't produce a GSR file in %s" % (self, self.outdir))
              return None
  
          # Open the GSR file.
          from abipy.electrons.gsr import GsrFile
          try:
              return GsrFile(gsr_path)
          except Exception as exc:
              logger.critical("Exception while reading GSR file at %s:\n%s" % (gsr_path, str(exc)))
              return None
docs: Open the GSR file located in the in self.outdir.
          Returns :class:`GsrFile` object, None if file could not be found or file is not readable.