Function _SetShapeInvariants

Set the shapes of the tensors in `enter_vars` to `shapes`. Args: input_vars: A list of tensors that are inputs to `enter_vars`. enter_vars: A list of tensors whose shapes will be set. shapes: A (possibly nested) list of shapes. Raises: ValueError: If any tensor in `enter_vars`

(input_vars, enter_vars, shapes)