Added support for the Loop operation in the MO IR Reader (#2971)

* Added support for the Loop operation in the MO IR Reader

model-optimizer/automation/package_BOM.txt

@@ -967,6 +967,7 @@ mo/utils/ir_reader/extenders/ExtractImagePatches_extender.py
 mo/utils/ir_reader/extenders/fakequantize_extender.py
 mo/utils/ir_reader/extenders/GRUCell_extender.py
 mo/utils/ir_reader/extenders/interpolate_extender.py
+mo/utils/ir_reader/extenders/loop_extender.py
 mo/utils/ir_reader/extenders/LSTMCell_extender.py
 mo/utils/ir_reader/extenders/non_max_suppression_extender.py
 mo/utils/ir_reader/extenders/non_zero_extender.py

model-optimizer/mo/utils/ir_reader/extenders/loop_extender.py

@@ -0,0 +1,62 @@
+"""
+ Copyright (C) 2018-2020 Intel Corporation
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+"""
+
+from mo.utils.graph import Node
+from mo.utils.ir_reader.extender import Extender
+from mo.utils.ir_reader.layer_to_class import copy_graph_with_ops
+
+
+class LoopExtender(Extender):
+    op = 'Loop'
+
+    @staticmethod
+    def extend(op: Node):
+        def normalize_port_map(port_map: dict):
+            for port in port_map:
+                for elem in ['axis', 'stride', 'part_size', 'start', 'end', 'purpose']:
+                    if port.get(elem) is None:
+                        port[elem] = None
+
+        assert op.has('body'), 'There is no "body" attribute in the Loop op {}.'.format(op.name)
+
+        # Now op.body is an IREngine, we need to replace it with IREngine.graph
+        op.body.graph.graph['cmd_params'] = op.graph.graph['cmd_params']
+        op.body.graph.graph['ir_version'] = op.graph.graph['ir_version']
+        op.body.graph.name = op.name + '/body'
+
+        for node in op.body.graph.get_op_nodes():
+            node['internal_layer_id'] = int(node.id)
+
+        op.body = copy_graph_with_ops(op.body.graph)
+
+        normalize_port_map(op.input_port_map)
+        normalize_port_map(op.output_port_map)
+
+        # the 'external_port_id' uses end-to-end numbering of ports, but at this moment it is separate for input and
+        # output ports so we need to decrease the output por_id with a number of input ports
+        for record in op.output_port_map:
+            if record['external_port_id'] != -1:
+                record['external_port_id'] -= len(op.in_ports())
+
+        for edge in op.back_edges:
+            edge['from_layer'] = edge['from-layer']
+            edge['to_layer'] = edge['to-layer']
+
+            edge['to_port'] = 0
+            edge['from_port'] = 0
+
+            del(edge['from-layer'])
+            del(edge['to-layer'])

model-optimizer/mo/utils/ir_reader/extenders/parameter_extender.py

@@ -13,7 +13,7 @@
  See the License for the specific language governing permissions and
  limitations under the License.
 """
-
+from mo.front.common.partial_infer.utils import int64_array
 from mo.middle.passes.convert_data_type import destination_type_to_np_data_type
 from mo.utils.graph import Node
 from mo.utils.ir_reader.extender import Extender
@@ -26,4 +26,7 @@ class Parameter_extender(Extender):
     def extend(op: Node):
         assert op.has_valid('element_type'), 'Parameter node {} has missed element_type attr!'.format(op.name)
         op['data_type'] = destination_type_to_np_data_type(op.element_type)
-        Extender.attr_to_list(op, 'shape')
+        if op.shape == '':
+            op.shape = int64_array([])
+        else:
+            Extender.attr_to_list(op, 'shape')