<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def path(self):
        "Returns the path up to the root for the current node."
        if self.parent:
            return '.'.join([self.parent.path, str(self.identifier)])
        else:
            return self.identifier if self.identifier else self.__class__.__name__