add onnx init file

server/visualdl/onnx/__init__.py

+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+from __future__ import unicode_literals
+
+import google.protobuf.message
+
+from .onnx_pb2 import ModelProto
+
+
+def load(obj):
+    '''
+    Loads a binary protobuf that stores onnx model
+
+    @params
+    Takes a file-like object (has "read" function)
+    or a string containing a file name
+    @return ONNX ModelProto object
+    '''
+    if hasattr(obj, 'read') and callable(obj.read):
+        s = obj.read()
+    else:
+        with open(obj, 'rb') as f:
+            s = f.read()
+    return load_from_string(s)
+
+
+def load_from_string(s):
+    '''
+    Loads a binary string that stores onnx model
+
+    @params
+    Takes a string object containing protobuf
+    @return ONNX ModelProto object
+    '''
+    model = ModelProto()
+    decoded = model.ParseFromString(s)
+    # in python implementation ParseFromString returns None
+    if decoded is not None and decoded != len(s):
+        raise google.protobuf.message.DecodeError(
+            "Protobuf decoding consumed too few bytes: {} out of {}".format(
+                decoded, len(s)))
+    return model