code: def check(self):
          
          st = self._stat()
          if self._st == st:
              return
  
          self._st = st
          self._remove_existing()
  
          if st is None:
              LOG.debug('%r: file has disappeared', self)
          else:
              self._on_file_changed()
docs: Compare the :func:`os.stat` for the pam_env style environmnt file
          `path` with the previous result `old_st`, which may be :data:`None` if
          the previous stat attempt failed. Reload its contents if the file has
          changed or appeared since last attempt.
  
          :returns:
              New :func:`os.stat` result. The new call to :func:`reload_env` should
              pass it as the value of `old_st`.