def get_output_shapes(self):
        """Get the shapes of the outputs."""
        outputs = self.execs[0].outputs
        shapes = [out.shape for out in outputs]

        concat_shapes = []
        for key, the_shape, axis in zip(self.symbol.list_outputs(), shapes, self.output_layouts):
            the_shape = list(the_shape)
            if axis >= 0:
                the_shape[axis] = self.batch_size
            concat_shapes.append((key, tuple(the_shape)))
        return concat_shapes
Get the shapes of the outputs.