[ONNX]onnx gather bug fix (#1543)

nnvm/python/nnvm/frontend/onnx.py

@@ -489,15 +489,11 @@ class Slice(OnnxOpConverter):
 class Gather(OnnxOpConverter):
     """ Operator converter for Gather.
     """
-
     @classmethod
     def _impl_v1(cls, inputs, attr, params):
-        axis = attr['axis']
-        indices = np.array(attr['indices'], dtype='int32')
-        name = 'gather_indices'
-        gather_indices = _sym.Variable(name=name, init=indices)
-        params[name] = indices
-        return _sym.take(inputs[0], gather_indices, axis=axis)
+        axis = attr.get('axis', 0)
+        return AttrCvt(op_name='take',
+                       extras={'axis':axis})(inputs, attr)
 
 class LRN(OnnxOpConverter):
     """ Operator converter for Local Response Normalization.