[OpenVINO backend] fix ops.slice (#21580)

* [OpenVINO backend] fix ops.slice

* add a simple test

* update comment

* modify test

Author: Mohamed-Ashraf273

keras/src/backend/openvino/core.py

@@ -843,9 +843,16 @@ def prepare_slice_index(val):
     start = ov_opset.concat(start, axis=0).output(0)
     stop = ov_opset.concat(stop, axis=0).output(0)
     axes = ov_opset.constant(axes, Type.i32).output(0)
-    return OpenVINOKerasTensor(
-        ov_opset.slice(inputs, start, stop, step, axes).output(0)
-    )
+    result = ov_opset.slice(inputs, start, stop, step, axes).output(0)
+
+    # Apply reshape to ensure output matches expected shape
+    # Convert None (dynamic) dimensions to -1 for OpenVINO compatibility
+    if all(dim is None or (isinstance(dim, int) and dim >= 0) for dim in shape):
+        reshape_pattern = [(-1 if dim is None else dim) for dim in shape]
+        target_shape = ov_opset.constant(reshape_pattern, Type.i32).output(0)
+        result = ov_opset.reshape(result, target_shape, False).output(0)
+
+    return OpenVINOKerasTensor(result)
 
 
 def slice_update(inputs, start_indices, updates):

keras/src/ops/core_test.py

@@ -645,6 +645,7 @@ def body(index, inputs, sum):
 
         index, inputs, sum = 0, np.arange(10), np.array([0])
         index, inputs, sum = core.while_loop(cond, body, (index, inputs, sum))
+        self.assertEqual(sum.shape, (1,))
         self.assertAllClose(sum, [45])
 
     def test_fori_loop(self):