tentative fix typechecking (2)

yt/visualization/_handlers.py

@@ -465,7 +465,7 @@ def _set_cmap(self, newval: "ColormapInput") -> None:
             self._cmap = newval
         elif isinstance(newval, str):
             self._cmap = mpl.colormaps[newval]
-        elif is_sequence(newval):
+        elif is_sequence(newval):  # type: ignore [unreachable]
             # tuple colormaps are from palettable (or brewer2mpl)
             self._cmap = get_brewer_cmap(newval)
         else: