docs: def load(self, callables_fname):
          r"""
          Load traced modules information from a `JSON <http://www.json.org/>`_ file.
  
          The loaded module information is merged with any existing module information
  
          :param callables_fname: File name
          :type  callables_fname: :ref:`FileNameExists`
  
          :raises:
           * OSError (File *[fname]* could not be found)
  
           * RuntimeError (Argument \\`callables_fname\\` is not valid)
          """
          # Validate file name
          _validate_fname(callables_fname)
          if not os.path.exists(callables_fname):
              raise OSError("File {0} could not be found".format(callables_fname))
          with open(callables_fname, "r") as fobj:
              fdict = json.load(fobj)
          if sys.hexversion < 0x03000000:  # pragma: no cover
              fdict = _unicode_to_ascii(fdict)
          self._callables_db.update(fdict["_callables_db"])
          # Reverse the tuple-to-string conversion that the save method
          # does due to the fact that JSON keys need to be strings and the
          # keys of the reverse callable dictionary are tuples where the first
          # item is a file name and the second item is the starting line of the
          # callable within that file (dictionary value)
          rdict = {}
          for key, value in fdict["_reverse_callables_db"].items():
              tokens = key[1:-1].split(",")
              key = tokens[0].strip()[1:-1]
              if platform.system().lower() == "windows":  # pragma: no cover
                  while True:
                      tmp = key
                      key = key.replace("\\\\", "\\")
                      if tmp == key:
                          break
              rdict[(key, int(tokens[1]))] = value
          self._reverse_callables_db.update(rdict)
          self._modules_dict.update(fdict["_modules_dict"])
          self._fnames.update(fdict["_fnames"])
          self._module_names.extend(fdict["_module_names"])
          self._class_names.extend(fdict["_class_names"])
          self._module_names = sorted(list(set(self._module_names)))
          self._class_names = sorted(list(set(self._class_names)))