Fix the bug of compile checkpoint to tensorrt

Closes #491

Signed-off-by: zhangkaili <zhang.kaili@zte.com.cn>

model_compiler/src/model_compiler/compilers/caffe_model_file_to_onnx_model.py

@@ -4,8 +4,6 @@
 import os
 from typing import Any, Mapping, NamedTuple, Optional, Sequence, List
 import numpy as np
-import caffe2.python.onnx.frontend
-from caffe2.proto import caffe2_pb2
 from . import repository
 from .. import utilities
 from ..models.data_format import DataFormat
@@ -48,6 +46,9 @@ def parse_caffe_net(net, pb_path):
 
 @repository.REPOSITORY.register(source_type=CaffeModelFile, target_type=OnnxModel, config_type=Config)
 def compile_source(source: CaffeModelFile, config: Config) -> OnnxModel:
+    from caffe2.python.onnx.frontend import caffe2_net_to_onnx_model  # pylint: disable=import-outside-toplevel
+    from caffe2.proto import caffe2_pb2  # pylint: disable=import-outside-toplevel
+
     predict_net = parse_caffe_net(caffe2_pb2.NetDef(), os.path.join(source.model_path, 'predict_net.pb'))
     predict_net.name = "model" if predict_net.name == "" else predict_net.name  # pylint: disable=no-member
     init_net = parse_caffe_net(caffe2_pb2.NetDef(), os.path.join(source.model_path, 'init_net.pb'))
@@ -57,7 +58,7 @@ def compile_source(source: CaffeModelFile, config: Config) -> OnnxModel:
         input_shape.insert(0, config.max_batch_size)
         value_info[config.input_names[i]] = (config.input_type, input_shape)
 
-    onnx_model = caffe2.python.onnx.frontend.caffe2_net_to_onnx_model(predict_net, init_net, value_info)
+    onnx_model = caffe2_net_to_onnx_model(predict_net, init_net, value_info)
 
     graph = onnx_model.graph  # pylint: disable=no-member
     return OnnxModel(model_proto=onnx_model,