Correcting type hints and black reformatting

puzzles/day06.py

@@ -18,22 +18,22 @@ class Reproduce:
     def __init__(self, times: List[int]) -> None:
         self.times = times
 
-    def start(self, days: int=80) -> None:
+    def start(self, days: int = 80) -> None:
         counts = Counter(self.times)
         for day in range(days):
-            next_counts = Counter() # Can't modify while iterating
+            next_counts = Counter()  # Can't modify while iterating
 
             for count_key, count in counts.items():
                 if count_key == 0:
-                    next_counts[6] += count # Move the parents back to 6 days
-                    next_counts[8] += count # Add the new fish
+                    next_counts[6] += count  # Move the parents back to 6 days
+                    next_counts[8] += count  # Add the new fish
                 else:
-                    next_counts[count_key - 1] += count # Move count to next day count
+                    next_counts[count_key - 1] += count  # Move count to next day count
 
             counts = next_counts
         self.time_counts = counts
 
-    def count_fish(self):
+    def count_fish(self) -> int:
         return sum(self.time_counts.values())