demos/py/human_pose_estimation/open_pose: don't rely on output_ops order in ng Function

The order for model converted with latest OpenVINO has changed

Author: Wovchena

demos/common/python/models/open_pose.py

@@ -36,9 +36,21 @@ def __init__(self, ie, model_path, target_size, aspect_ratio, prob_threshold, si
 
         function = ng.function_from_cnn(self.net)
         paf = function.get_output_op(0)
+        paf_shape = paf.outputs()[0].get_shape()
+        heatmap = function.get_output_op(1)
+        heatmap_shape = heatmap.outputs()[0].get_shape()
+        if len(paf_shape) != 4 and len(heatmap_shape) != 4:
+            raise RuntimeError('OpenPose outputs must be 4-dimensional')
+        if paf_shape[2] != heatmap_shape[2] and paf_shape[3] != heatmap_shape[3]:
+            raise RuntimeError('Last two dimensions of OpenPose outputs must match')
+        if paf_shape[1] * 2 == heatmap_shape[1]:
+            paf, heatmap = heatmap, paf
+        elif paf_shape[1] != heatmap_shape[1] * 2:
+            raise RuntimeError('Size of second dimension of OpenPose of one output must be two times larger then size '
+                'of second dimension of another output')
+
         paf = paf.inputs()[0].get_source_output().get_node()
         paf.set_friendly_name(self.pafs_blob_name)
-        heatmap = function.get_output_op(1)
         heatmap = heatmap.inputs()[0].get_source_output().get_node()
         heatmap.set_friendly_name(self.heatmaps_blob_name)