Added support for mutable hash tables and fixed bug in making string constants (#1282)

Signed-off-by: Tom Wildenhain <[email protected]>

Author: TomWildenhain-Microsoft

tf2onnx/graph.py

@@ -558,7 +558,7 @@ def make_const(self, name, np_val, skip_conversion=False, raw=True):
             skip_conversion: bool, indicate whether this created node would be mapped during conversion.
             raw: whether to store data at field of raw_data or the specific field according to its dtype
         """
-        if raw:
+        if raw and np_val.dtype != np.object:
             onnx_tensor = numpy_helper.from_array(np_val, name)
         else:
             onnx_tensor = helper.make_tensor(name, utils.map_numpy_to_onnx_dtype(np_val.dtype),

tf2onnx/tf_utils.py

@@ -293,7 +293,7 @@ def get_hash_table_info(nodes_or_graph_def):
     key_dtypes = []
     val_dtypes = []
     for n in nodes:
-        if n.op == "HashTableV2":
+        if n.op in ["HashTableV2", "MutableHashTableV2"]:
             if all(k in n.attr for k in ['shared_name', 'key_dtype', 'value_dtype']):
                 name = n.attr['shared_name'].s
                 if name != b'':