input: Write a python function to multiply two matrices.
  assert multiply_matrices([[1, 2], [3, 4]], [[2, 0], [1, 2]]) == [[4, 4], [10, 8]]
  assert multiply_matrices([[1, 0, 2], [-1, 3, 1]], [[3, 1], [2, 1], [1, 0]]) == [[5, 1], [1, 2]]
  assert multiply_matrices([[2, 4], [3, 4]], [[1, 2], [1, 3]]) == [[6, 16], [7, 18]]
output: def multiply_matrices(A, B):
      rows_A = len(A)
      cols_A = len(A[0])
      cols_B = len(B[0])
      
      result = [[0 for _ in range(cols_B)] for _ in range(rows_A)]
      
      for i in range(rows_A):
          for j in range(cols_B):
              for k in range(cols_A):
                  result[i][j] += A[i][k] * B[k][j]
                  
      return result