Relay.frontend.form_onnx return empty params

hi, i’m new here, i use the fllow code

onnx_graph = onnx.load(open(onnx_path, "rb"))
data_shape = (batch_size, 3, 224, 224)
mod, params = relay.frontend.from_onnx(onnx_graph, {"data": data_shape})
with tvm.transform.PassContext(opt_level=3):
    qfunc = relay.quantize.prerequisite_optimize(mod, params=params)
           with tvm.autotvm.apply_history_best(logfile):
                qfunc = qtz.quantize(qfunc, params, dataset=dataset)

but the length of params returned by relay.frontend.from_onnx is zero. for weight quant, no params is ok?