This is part of #8362 - I'm hoping to break down that PR into easier-to-review chunks.

1. A tile's args might be a tuple, string or None.
   

   	class _Tile(NamedTuple):
   	codec_name: str
   	extents: tuple[int, int, int, int] | None
   	offset: int = 0
   	args: tuple[Any, ...] | str | None = None

   
   Assert that args is a tuple before accessing a value by index.

2. _getmp may return a dict or None.
   

   def _getmp(self) -> dict[int, Any] | None:

   
   Assert that it is not None before using a key.

3. Pixel access might return a tuple or a float.
   

   	class PixelAccess:
   	def __getitem__(self, xy: tuple[int, int]) -> float | tuple[int, ...]: ...

   
   Assert that it is a tuple before checking one of the channel values.

4. load() might return None.
   

   def load(self) -> core.PixelAccess | None:

   
   Assert that it isn't None before getting pixel data for a particular co-ordinate.

5. getcolors() might return None.
   

   	def getcolors(
   	self, maxcolors: int = 256
   	) -> list[tuple[int, tuple[int, ...]]] | list[tuple[int, float]] | None:

   
   Assert that it isn't None before checking how much a colour is used.