code: def open(cls, filename):
          
          filename = os.path.expanduser(filename)
          f = open(filename, 'r')
          if _can_ujson:
              # NOTE: this will not parse the unicode.  Bundle.open always calls
              # json instead of ujson for this reason.
              data = ujson.load(f)
          else:
              data = json.load(f, object_pairs_hook=parse_json)
          f.close()
          return cls(data)
docs: Open a ParameterSet from a JSON-formatted file.
          This is a constructor so should be called as:
  
  
          >>> b = ParameterSet.open('test.json')
  
  
          :parameter str filename: relative or full path to the file
          :return: instantiated :class:`ParameterSet` object