<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def load_model(file_path):
 """ Loads an ONNX model to a ProtoBuf object. :param file_path: ONNX file (full file name) :return: ONNX model. Example: :: from onnxmltools.utils import load_model onnx_model = load_model("SqueezeNet.onnx") """

    if not path.exists(file_path):
        raise FileNotFoundError("{0} was not found.".format(file_path))
    model = onnx_proto.ModelProto()
    with open(file_path, 'rb') as f:
        model.ParseFromString(f.read())
    return model