docs: def _load_ssh_file(self, path):
          """
          Attempt to open and parse an SSH config file at ``path``.
  
          Does nothing if ``path`` is not a path to a valid file.
  
          :returns: ``None``.
          """
          if os.path.isfile(path):
              old_rules = len(self.base_ssh_config._config)
              with open(path) as fd:
                  self.base_ssh_config.parse(fd)
              new_rules = len(self.base_ssh_config._config)
              msg = "Loaded {} new ssh_config rules from {!r}"
              debug(msg.format(new_rules - old_rules, path))
          else:
              debug("File not found, skipping")