fix(frontend-python): mimic summing like numpy exactly

frontends/concrete-python/concrete/fhe/tracing/tracer.py

@@ -465,6 +465,12 @@ class Tracer:
             sanitized_args = [self.sanitize(args[0])]
             if len(args) > 1:
                 kwargs["newshape"] = args[1]
+        elif func is np.sum:
+            sanitized_args = [self.sanitize(args[0])]
+            for i, keyword in enumerate(["axis", "dtype", "out", "keepdims", "initial", "where"]):
+                position = i + 1
+                if len(args) > position:
+                    kwargs[keyword] = args[position]
         elif func is np.transpose:
             sanitized_args = [self.sanitize(args[0])]
             if len(args) > 1:

frontends/concrete-python/tests/execution/test_sum.py

@@ -17,6 +17,18 @@ from concrete import fhe
                 "x": {"shape": (3, 2), "range": [0, 10], "status": "encrypted"},
             },
         ),
+        pytest.param(
+            lambda x: np.sum(x, 0),
+            {
+                "x": {"shape": (3, 2), "range": [0, 10], "status": "encrypted"},
+            },
+        ),
+        pytest.param(
+            lambda x: np.sum(x, 1),
+            {
+                "x": {"shape": (3, 2), "range": [0, 10], "status": "encrypted"},
+            },
+        ),
         pytest.param(
             lambda x: np.sum(x, axis=None),  # type: ignore
             {