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:
  # Test case 1: Initializing and printing a matrix
  mat1 = Matrix(2, 2, [1, 2, 3, 4])
  print(mat1)
  # Expected output:
  # 1 2 
  # 3 4 
  
  # Test case 2: Matrix addition
  mat2 = Matrix(2, 2, [5, 6, 7, 8])
  mat1.add(mat2)
  print(mat1)
  # Expected output:
  # 6 8 
  # 10 12 
  
  # Test case 3: Matrix subtraction
  mat1 = Matrix(2, 2, [1, 2, 3, 4])
  mat2 = Matrix(2, 2, [5, 6, 7, 8])
  mat1.sub(mat2)
  print(mat1)
  # Expected output:
  # -4 -4 
  # -4 -4 
  
  # Test case 4: Matrix multiplication
  mat1 = Matrix(2, 3, [1, 2, 3, 4, 5, 6])
  mat2 = Matrix(3, 2, [7, 8, 9, 10, 11, 12])
  mat1.mul(mat2)
  print(mat1)
  # Expected output:
  # 58 64 
  # 139 154 
  
  # Test case 5: Matrix transpose
  mat1 = Matrix(2, 3, [1, 2, 3, 4, 5, 6])
  mat1.transpose()
  print(mat1)
  # Expected output:
  # 1 4 
  # 2 5 
  # 3 6 
  
output:     
      def scalar_mul(self, scalar):
          for i in range(self.m):
              for j in range(self.n):
                  self.mat[i][j] *= scalar
  
      def get_element(self, i, j):
          return self.mat[i][j]
  
      def set_element(self, i, j, value):
          self.mat[i][j] = value
  
      def is_square(self):
          return self.m == self.n
  
      def is_symmetric(self):
          if not self.is_square():
              return False
          for i in range(self.m):
              for j in range(i + 1, self.n):
                  if self.mat[i][j] != self.mat[j][i]:
                      return False
          return True
  