code: def get_config_var(self, path, env=None):
          '''
          retrieves the config variable named ``path`` from the config file.
          Path elements that start with a $ are replaced with values from the
          dict passed as ``env``
          '''
          if env is None:
              env = {}
          result = self.conf
          for e in path.split('.'):
              if e[0] == '$':
                  try:
                      result = result[env[e[1:]]]
                  except KeyError as ex:
                      try:
                          result = result['.default']
                      except KeyError:
                          raise ex
              else:
                  result = result[e]
          return resulf get_config_var(self, path, env=None):
          '''
          retrieves the config variable named ``path`` from the config file.
          Path elements that start with a $ are replaced with values from the
          dict passed as ``env``
          '''
          if env is None:
              env = {}
          result = self.conf
          for e in path.split('.'):
              if e[0] == '$':
                  try:
                      result = result[env[e[1:]]]
                  except KeyError as ex:
                      try:
                          result = result['.default']
                      except KeyError:
                          raise ex
              else:
                  result = result[e]
          return result
docs: retrieves the config variable named ``path`` from the config file.
          Path elements that start with a $ are replaced with values from the
          dict passed as ``env``