<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def peek(self, iroute: "InstanceRoute") -> Optional[Value]: """Return a value within the receiver's subtree. Args: iroute: Instance route (relative to the receiver). """

        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