I don't think this is right. I think you mean:

```
if not isinstance(funcs, (tuple, list)):
    funcs = (funcs,)
if not funcs:
    funcs = tuple(L.atoms(Function))
else:
    for f in funcs:
       if not isinstance(f, Function):
           raise TypeError('Function expected, got: %s' % f)  # or %r -- I don't know the difference
```