input: 
  class Matrix:
      def __init__(self, m, n, lst):
          self.m = m
          self.n = n
          self.mat = []
  
          c = 0
          for i in range(self.m):
              a = []
              for j in range(self.n):
                  a.append(lst[c])
                  c += 1
              self.mat.append(a)
  
      def __str__(self):
          output = ""
          for i in self.mat:
              for j in i:
                  output += str(j) + " "
              output += '\n'
          return output
  
      def add(self, mat2):
          for i in range(self.m):
              for j in range(self.n):
                  self.mat[i][j] += mat2.mat[i][j]
  
      def sub(self, mat2):
          for i in range(self.m):
              for j in range(self.n):
                  self.mat[i][j] -= mat2.mat[i][j]
  
      def mul(self, mat2):
          result = []
          for i in range(self.m):
              a = []
              for j in range(mat2.n):
                  s = 0
                  for k in range(self.n):
                      s += self.mat[i][k] * mat2.mat[k][j]
                  a.append(s)
              result.append(a)
          self.mat = result
          self.m = len(result)
          self.n = len(result[0])
  
      def transpose(self):
          result = [[self.mat[j][i] for j in range(len(self.mat))] for i in range(len(self.mat[0]))]
          self.mat = result
          self.m = len(result)
          self.n = len(result[0])
  
  # Test cases:
  # Example 1:
  # Input: m = 2, n = 2, lst = [1, 2, 3, 4]
  # Creating matrix:
  # 1 2 
  # 3 4 
  # Addition with itself:
  # 2 4 
  # 6 8 
  # Substraction with itself:
  # 0 0 
  # 0 0 
  # Transpose:
  # 1 3 
  # 2 4 
  # Multiplication with itself:
  # 7 10 
  # 15 22 
  
output:     
      def __eq__(self, other):
          if self.m != other.m or self.n != other.n:
              return False
          for i in range(self.m):
              for j in range(self.n):
                  if self.mat[i][j] != other.mat[i][j]:
                      return False
          return True
  