code: def get_from_layer(self, name, layer=None):
          
          if name not in self._children:
              if self._frozen:
                  raise KeyError(name)
              self._children[name] = ConfigTree(layers=self._layers)
          child = self._children[name]
          if isinstance(child, ConfigNode):
              return child.get_value(layer)
          else:
              return child
docs: Get a configuration value from the named layer.
  
          Parameters
          ----------
          name : str
              The name of the value to retrieve
          layer: str
              The name of the layer to retrieve the value from. If it is not supplied
              then the outermost layer in which the key is defined will be used.