I have the following code:

  def g(input: Mapping[str, str | Sequence[tuple[str, str]] | Sequence[str]) -> bool: 
     ...

  def main():
     ...
     mydict: dict[str, str] = ...
     mylist: list[str] = ...
     mystring: str = ...
     context = {
      'a': [x for x in mylist if f(x)],
      'b': list(mydict.items())
      'c': mystring,
      }
      g(context)

mypy complains about this code, saying that Argument 2 to "g" has incompatible type "dict[str, object]"; expected "Mapping[str, Sequence[tuple[str, str]] | Sequence[str] | str]"

If I remove the b key, then it works fine - apparently mypy can tell that context is a dict[str, str | list[str]] and thus compatible with the signature for g. But if I add the b key, it gives up and infers a generic dict[str, object] type, which is then incompatible with g.

Worth noting that the type is correctly inferred by Pylance integrated with vscode.