Replace all dimensions with negative values to batch size

def replace_negative_size_with_batch_size(shape, batch_size):
    """Replace all dimensions with negative values to batch size"""
    sl = []
    for d in shape.dim:
        if d < 0:
            # Negative size means batch size
            sl.append(batch_size)
        else:
            sl.append(d)
    out_shape = nnabla_pb2.Shape()
    out_shape.dim.extend(sl)
    return out_shape