Arm backend: Replace asserts with exceptions in permutation code

Refactor assertion statements to raise ValueErrors for better error
handling in permutation matrix and vector transformations. Ensure that
conditions are checked and appropriate exceptions are raised to enhance
code robustness and readability.

Signed-off-by: Sebastian Larsson <[email protected]>
Change-Id: Ia2816024504b0c31adb3474be26e1a710ee10aa2

Author: Sebastian-Larsson

backends/arm/operators/op_permute.py

@@ -46,24 +46,26 @@ def permutation_matrix_to_vector(permutation_matrix: torch.Tensor) -> list[int]:
     (1,0,2)
     """
     N = len(permutation_matrix)
-    assert N == len(
-        permutation_matrix[0]
-    ), f"A permutation matrix must be square, got shape {permutation_matrix.shape}"
+    if N != len(permutation_matrix[0]):
+        raise ValueError(
+            f"A permutation matrix must be square, got shape {permutation_matrix.shape}"
+        )
 
     p = [0] * N
     for row_index, row in enumerate(permutation_matrix):
         saw_one = False
         for col_index, value in enumerate(row):
             if value == 1:
-                assert (
-                    not saw_one
-                ), f"A permutation matrix can only have one 1 per row, got row {row}."
+                if saw_one:
+                    raise ValueError(
+                        f"A permutation matrix can only have one 1 per row, got {row=}"
+                    )
                 p[row_index] = col_index
                 saw_one = True
-            else:
-                assert (
-                    value == 0
-                ), f"A permutation matrix only contains 1's and 0's, got value {value}."
+            elif value != 0:
+                raise ValueError(
+                    f"A permutation matrix only contains 1's and 0's, got {value=}"
+                )
     return p