fix pytest-dev#11797: be more lenient on SequenceLike approx

this needs a validation as it allows partially implemented sequences

changelog/11797.bugfix.rst

@@ -0,0 +1 @@
+Ensure approx for SequenceLike objects doesn't wrap those sequences in a scalar.

src/_pytest/python_api.py

@@ -128,6 +128,8 @@ def _recursive_sequence_map(f, x):
     if isinstance(x, (list, tuple)):
         seq_type = type(x)
         return seq_type(_recursive_sequence_map(f, xi) for xi in x)
+    elif _is_sequence_like(x):
+        return [_recursive_sequence_map(f, xi) for xi in x]
     else:
         return f(x)
 
@@ -721,12 +723,7 @@ def approx(expected, rel=None, abs=None, nan_ok: bool = False) -> ApproxBase:
     elif _is_numpy_array(expected):
         expected = _as_numpy_array(expected)
         cls = ApproxNumpy
-    elif (
-        hasattr(expected, "__getitem__")
-        and isinstance(expected, Sized)
-        # Type ignored because the error is wrong -- not unreachable.
-        and not isinstance(expected, STRING_TYPES)  # type: ignore[unreachable]
-    ):
+    elif _is_sequence_like(expected):
         cls = ApproxSequenceLike
     elif (
         isinstance(expected, Collection)
@@ -741,6 +738,15 @@ def approx(expected, rel=None, abs=None, nan_ok: bool = False) -> ApproxBase:
     return cls(expected, rel, abs, nan_ok)
 
 
+def _is_sequence_like(expected: object) -> bool:
+    return (
+        hasattr(expected, "__getitem__")
+        and isinstance(expected, Sized)
+        # Type ignored because the error is wrong -- not unreachable.
+        and not isinstance(expected, STRING_TYPES)  # type: ignore[unreachable]
+    )
+
+
 def _is_numpy_array(obj: object) -> bool:
     """
     Return true if the given object is implicitly convertible to ndarray,