<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def fail_stop(self):
 """ Explicit stop-the-build failure. This sets failure status on the target nodes and all of their dependent parent nodes. Note: Although this function is normally invoked on nodes in the executing state, it might also be invoked on up-to-date nodes when using Configure(). """

        T = self.tm.trace
        if T: T.write(self.trace_message('Task.failed_stop()', self.node))

        # Invoke will_not_build() to clean-up the pending children
        # list.
        self.tm.will_not_build(self.targets, lambda n: n.set_state(NODE_FAILED))

        # Tell the taskmaster to not start any new tasks
        self.tm.stop()

        # We're stopping because of a build failure, but give the
        # calling Task class a chance to postprocess() the top-level
        # target under which the build failure occurred.
        self.targets = [self.tm.current_top]
        self.top = 1