def load_param(params, ctx=None):
    """same as mx.model.load_checkpoint, but do not load symnet and will convert context"""
    if ctx is None:
        ctx = mx.cpu()
    save_dict = mx.nd.load(params)
    arg_params = {}
    aux_params = {}
    for k, v in save_dict.items():
        tp, name = k.split(':', 1)
        if tp == 'arg':
            arg_params[name] = v.as_in_context(ctx)
        if tp == 'aux':
            aux_params[name] = v.as_in_context(ctx)
    return arg_params, aux_params
same as mx.model.load_checkpoint, but do not load symnet and will convert context