Unsupported target for indexed assignment

Question

Function runs perfectly, but I am getting error with mypy:

Unsupported target for indexed assignment

Here is my code:

def function(image: List[str], start: Tuple[int]):
    if image[start[0]][start[1]] == "*":
        return
    else:
        image[start[0]][start[1]] = "*"
        if start[0] > 0:
            function(image, [start[0]-1, start[1]])
        if start[0] < len(image) - 1:
            function(image, [start[0]+1, start[1]])
        if start[1] > 0:
            function(image, [start[0], start[1]-1])
        if start[1] < len(image) - 1:
            function(image, [start[0], start[1]+1])

The mistake is in line:

image[start[0]][start[1]] = "*"

image = ["*", "."] start = (1, 1) - tuple contains coordinates.

Answer 1

self._balances:Mapping[str,Optional[float]]

If anyone comes here because of using Mapping, use MutableMapping instead, because you can only assign values to a mutable object

self._balances:MutableMapping[str,Optional[float]]

Answer 2

Problem solved.
The correct types are:

image: List[List[str]], start: Tuple[int, int]