docs: def reload (self, filename=None, data=None):
          """Reloads the a AIT configuration.
  
          The AIT configuration is automatically loaded when the AIT
          package is first imported.  To replace the configuration, call
          reload() (defaults to the current config.filename) or
          reload(new_filename).
          """
          if data is None and filename is None:
              filename = self._filename
  
          self._config   = loadYAML(filename, data)
          self._filename = filename
  
          if self._config is not None:
              keys         = 'default', self._platform, self._hostname
              self._config = flatten(self._config, *keys)
  
              # on reload, if pathvars have not been set, we want to start
              # with the defaults, add the platform and hostname, and
              # merge in all of the information provided in the config
              if self._pathvars is None:
                  self._pathvars = self.getDefaultPathVariables()
  
              expandConfigPaths(self._config, 
                              self._directory,
                              self._datetime,
                              merge(self._config, self._pathvars))
  
          else:
              self._config = { }