def METHOD_NAME(func: Callable) -> List[Tuple[Signature, Any]]:
    """Find all available implementations for a fused cython function."""
    impls = []
    mod = importlib.import_module(func.__module__)
    signatures = getattr(func, "__signatures__", None)
    if signatures is not None:
        # Cython function with __signatures__ should be fused and thus
        # indexable
        func_map = cast(Mapping, func)
        candidates = [func_map[key] for key in signatures]
    else:
        candidates = [func]
    for candidate in candidates:
        name = candidate.__name__
        capsule = mod.__pyx_capi__[name]
        llc = LowLevelCallable(capsule)
        try:
            signature = Signature.from_c_types(llc.signature.encode())
        except KeyError:
            continue
        impls.append((signature, capsule))
    return impls