Add helper function _constant in onnx.py
diff --git a/torch/onnx.py b/torch/onnx.py
index 3494a1c..810a377 100644
--- a/torch/onnx.py
+++ b/torch/onnx.py
@@ -190,5 +190,37 @@
     return self.op("ATen", *args, operator_s=opname, **kwargs)
 
 
+def _constant(self, value, dims, type=None, *args, **kwargs):
+    assert(isinstance(value, (int, long, float)))
+    # Infer the type based on value.
+    if type is None:
+        if isinstance(value, int):
+            type = "int"
+        elif isinstance(value, long):
+            type = "long"
+        elif isinstance(value, float):
+            type = "float"
+
+    if type == "char":
+        tensor = torch.CharTensor(*dims)
+    elif type == "short":
+        tensor = torch.ShortTensor(*dims)
+    elif type == "int":
+        tensor = torch.IntTensor(*dims)
+    elif type == "long":
+        tensor = torch.LongTensor(*dims)
+    elif type == "half":
+        tensor = torch.HalfTensor(*dims)
+    elif type == "float":
+        tensor = torch.FloatTensor(*dims)
+    elif type == "double":
+        tensor = torch.DoubleTensor(*dims)
+    else:
+        raise ValueError("Unknown type, type should be one of the following strings:"
+                         "char, short, int, long, half, float, double")
+    tensor.fill_(value)
+    return self.op("Constant", *args, value_t=tensor, **kwargs)
+
 torch._C.Graph.op = _op
 torch._C.Graph.at = _at
+torch._C.Graph.constant = _constant