Added extractor for ONNX operation Size (#6031)

* Added extractor for ONNX operation Size

* Moved transformation of Size operation from TF specific to generic front phase

* Updated list of supported ONNX operation

* Moved unit test for Size decomposition to a new location

docs/MO_DG/prepare_model/Supported_Frameworks_Layers.md

@@ -500,6 +500,7 @@ Standard ONNX\* operators:
 | Sigmoid | No |
 | Sign | No |
 | Sin | No |
+| Size | No |
 | Slice | No |
 | Softmax | No |
 | Softplus | No |

model-optimizer/automation/package_BOM.txt

@@ -338,6 +338,7 @@ extensions/front/onnx/roialign_ext.py
 extensions/front/onnx/roifeatureextractor_ext.py
 extensions/front/onnx/scatter_ext.py
 extensions/front/onnx/shape_ext.py
+extensions/front/onnx/size_ext.py
 extensions/front/onnx/slice_ext.py
 extensions/front/onnx/softmax_ext.py
 extensions/front/onnx/softmaxONNX_to_softmax.py
@@ -363,6 +364,7 @@ extensions/front/reshape_dim_normalizer.py
 extensions/front/restore_ports.py
 extensions/front/RollWithEmptyAxesReplacer.py
 extensions/front/scatter_normalizer.py
+extensions/front/SizeReplacer.py
 extensions/front/softmax.py
 extensions/front/Softplus_fusion.py
 extensions/front/softsign_replacer.py
@@ -483,7 +485,6 @@ extensions/front/tf/roll_ext.py
 extensions/front/tf/RollRealImagPack.py
 extensions/front/tf/select_ext.py
 extensions/front/tf/sign_ext.py
-extensions/front/tf/SizeReplacer.py
 extensions/front/tf/slice_ext.py
 extensions/front/tf/softmax_ext.py
 extensions/front/tf/softplus_ext.py

model-optimizer/extensions/front/onnx/size_ext.py

@@ -0,0 +1,17 @@
+# Copyright (C) 2018-2021 Intel Corporation
+# SPDX-License-Identifier: Apache-2.0
+
+import numpy as np
+
+from extensions.ops.size import Size
+from mo.front.extractor import FrontExtractorOp
+
+
+class SizeExtractor(FrontExtractorOp):
+    op = 'Size'
+    enabled = True
+
+    @classmethod
+    def extract(cls, node):
+        Size.update_node_stat(node, {'output_type': np.int64})
+        return cls.enabled

model-optimizer/extensions/ops/size.py

@@ -9,6 +9,7 @@ from mo.ops.op import Op
 
 class Size(Op):
     op = 'Size'
+    enabled = False
 
     def __init__(self, graph: Graph, attrs: dict):
         assert 'output_type' in attrs, 'Size has mandatory `output_type` attribute'

model-optimizer/unit_tests/extensions/front/size_replacer_test.py

@@ -6,7 +6,7 @@ import unittest
 import numpy as np
 from generator import generator, generate
 
-from extensions.front.tf.SizeReplacer import SizeFrontReplacer
+from extensions.front.SizeReplacer import SizeFrontReplacer
 from mo.front.common.partial_infer.utils import int64_array
 from mo.utils.ir_engine.compare_graphs import compare_graphs
 from unit_tests.utils.graph import build_graph, regular_op_with_empty_data, result, connect, \