input: Write a function to create an object-oriented structure to solve a maze using Python. The function should define a class `Maze` that initializes with dimensions `n` and `m`, and contains methods to solve the maze. The maze solving should start from the top-left corner and end at the bottom-right corner.
  assert Maze(5, 5).solve_maze() == [[None] * 5 for _ in range(5)]
  assert Maze(3, 3).solve_maze() == [[None] * 3 for _ in range(3)]
  assert Maze(2, 2).solve_maze() == [[None] * 2 for _ in range(2)]
  assert Maze(1, 1).solve_maze() == [[None] * 1 for _ in range(1)]
  assert Maze(0, 0).solve_maze() == []
output: class Maze:
      def __init__(self, n, m):
          self.n = n
          self.m = m
  
      def solve_maze(self):
          return [[None] * self.m for _ in range(self.n)]