'The analysis routine that runs on each node in the graph.
:param node:    A node in the graph.
:param state:   An abstract state that acts as the initial abstract state of this analysis routine.
:return:        A tuple: (changed, output abstract state)'

def _run_on_node(self, node, state):

    raise NotImplementedError('_run_on_node()    is    not    implemented.')
