code: def peek(self, iroute: "InstanceRoute") -> Optional[Value]:
          
          val = self.value
          sn = self.schema_node
          for sel in iroute:
              val, sn = sel.peek_step(val, sn)
              if val is None:
                  return None
          return val
docs: Return a value within the receiver's subtree.
  
          Args:
              iroute: Instance route (relative to the receiver).