def __init__(self, shapes):
        """
        Args:
            shapes (list[list]): a list of fully-specified shapes.
        """
        self.shapes = shapes
        logger.warn("Using dummy input for debug!")

        def fn():
            tlist = []
            ctx = get_current_tower_context()
            assert ctx is not None
            assert len(self.shapes) == len(self._spec)
            for idx, p in enumerate(self._spec):
                tlist.append(tf.constant(
                    0, dtype=p.dtype,
                    name='dummy-{}-{}'.format(p.name, ctx.index),
                    shape=self.shapes[idx]))
            return tlist
        super(DummyConstantInput, self).__init__(fn)

        Args:
            shapes (list[list]): a list of fully-specified shapes.
        
tensorpack/input_source/input_source.py