def validate(self, fgraph):
        if self.destroyers:
            ords = self.orderings(fgraph)

            if _contains_cycle(fgraph, ords):
                raise InconsistencyError("Dependency graph contains cycles")
        else:
            # James's Conjecture:
            # If there are no destructive ops, then there can be no cycles.

            # FB: This isn't always True. It can happend that
            # optimization introduce node that depend on itself. This
            # is very rare and should not happen in general. It will be
            # caught later. The error will be far from the source. But
            # doing this conjecture should speed up compilation most of
            # the time. The user should create such dependency except
            # if he mess too much with the internal.
            pass
        return True
Return None.
dataset/ETHPy150Open rizar/attention-lvcsr/libs/Theano/theano/gof/destroyhandler.py/DestroyHandler.validate