Fix linting.

src/holt59/aoc/2022/day12.py

@@ -122,8 +122,8 @@ lines = sys.stdin.read().splitlines()
 
 grid = [[ord(cell) - ord("a") for cell in line] for line in lines]
 
-start: tuple[int, int]
-end: tuple[int, int]
+start: tuple[int, int] | None = None
+end: tuple[int, int] | None = None
 
 # for part 2
 start_s: list[tuple[int, int]] = []
@@ -138,6 +138,9 @@ for i_row, row in enumerate(grid):
         elif col == 0:
             start_s.append((i_row, i_col))
 
+assert start is not None
+assert end is not None
+
 # fix values
 grid[start[0]][start[1]] = 0
 grid[end[0]][end[1]] = ord("z") - ord("a")