Extend nGraph for operation GatherND-5 and implement reference (#2587)

Signed-off-by: Roman Kazantsev <roman.kazantsev@intel.com>

ngraph/python/tests/test_ngraph/test_data_movement.py

@@ -17,6 +17,7 @@ import numpy as np
 import pytest
 
 import ngraph as ng
+from ngraph.impl import Type
 from tests.runtime import get_runtime
 from tests.test_ngraph.util import run_op_node
 
@@ -199,3 +200,18 @@ def test_select():
 
     result = run_op_node([cond, then_node, else_node], ng.select)
     assert np.allclose(result, excepted)
+
+
+def test_gather_nd():
+    indices_type = np.int32
+    data_dtype = np.float32
+    data = ng.parameter([2, 10, 80, 30, 50], dtype=data_dtype, name="data")
+    indices = ng.parameter([2, 10, 30, 40, 2], dtype=indices_type, name="indices")
+    batch_dims = 2
+    expected_shape = [20, 30, 40, 50]
+
+    node = ng.gather_nd(data, indices, batch_dims)
+    assert node.get_type_name() == "GatherND"
+    assert node.get_output_size() == 1
+    assert list(node.get_output_shape(0)) == expected_shape
+    assert node.get_output_element_type(0) == Type.f32