refactor: annotate method return type

Add missing annotations for methods that return None.

cell.py

@@ -11,7 +11,7 @@ class Cell:
             x1: int, y1: int,
             x2: int, y2: int,
             window: Window
-    ):
+    ) -> None:
         # Define the cell walls
         top_wall = Line(Point(x1, y1), Point(x2, y1))
         bottom_wall = Line(Point(x1, y2), Point(x2, y2))
@@ -37,7 +37,7 @@ class Cell:
             bottom: bool = True,
             left: bool = True,
             right: bool = True,
-    ):
+    ) -> None:
         """
         configure_walls configures the existence of the Cell's walls.
         """
@@ -52,7 +52,7 @@ class Cell:
         """
         return self.__centre
 
-    def draw(self):
+    def draw(self) -> None:
         """
         draw draws the cell onto the canvas
         """
@@ -65,7 +65,7 @@ class Cell:
         if self.__right_wall.exists:
             self.__window.draw_line(self.__right_wall.line)
 
-    def draw_move(self, to_cell: 'Cell', undo: bool = False):
+    def draw_move(self, to_cell: 'Cell', undo: bool = False) -> None:
         """
         draw_move draws a path between the centre of this cell and
         the centre of the given cell.
@@ -83,6 +83,6 @@ class CellWall:
     a Cell's wall.
     """
 
-    def __init__(self, line: Line):
+    def __init__(self, line: Line) -> None:
         self.exists = True
         self.line = line

graphics.py

@@ -16,11 +16,11 @@ class Line:
     Line represents a graphical line.
     """
 
-    def __init__(self, point_a: Point, point_b: Point):
+    def __init__(self, point_a: Point, point_b: Point) -> None:
         self.point_a = point_a
         self.point_b = point_b
 
-    def draw(self, canvas: Canvas, fill_colour: str):
+    def draw(self, canvas: Canvas, fill_colour: str) -> None:
         """
         draw draws a line on a given canvas.
         """
@@ -37,7 +37,7 @@ class Window:
     Window is a Graphical window.
     """
 
-    def __init__(self, width: int, height: int):
+    def __init__(self, width: int, height: int) -> None:
         self.__root = Tk()
         self.__root.title("Maze Solver")
         self.__root.protocol("WM_DELETE_WINDOW", self.close)
@@ -59,14 +59,14 @@ class Window:
 
         self.__is_running = False
 
-    def redraw(self):
+    def redraw(self) -> None:
         """
         redraw redraws all the graphics in the window.
         """
         self.__root.update_idletasks()
         self.__root.update()
 
-    def wait_for_close(self):
+    def wait_for_close(self) -> None:
         """
         wait_for_close continuously redraws the window until
         it is set to close.
@@ -75,13 +75,13 @@ class Window:
         while self.__is_running:
             self.redraw()
 
-    def draw_line(self, line: Line, fill_colour: str = "black"):
+    def draw_line(self, line: Line, fill_colour: str = "black") -> None:
         """
         draw_line draws a line on the canvas.
         """
         line.draw(self.__canvas, fill_colour)
 
-    def close(self):
+    def close(self) -> None:
         """
         close sets the window to close.
         """