input: Write a function to multiply two matrices.
  assert multiply_matrices([[1, 2], [3, 4]], [[5, 6], [7, 8]]) == [[19, 22], [43, 50]]
  assert multiply_matrices([[1, 0], [0, 1]], [[4, 5], [6, 7]]) == [[4, 5], [6, 7]]
  assert multiply_matrices([[2, 3, 4], [1, 0, 0]], [[0, 1000], [1, 100], [0, 10]]) == [[3, 2340], [0, 1000]]
output: def multiply_matrices(A, B):
      # Number of rows in A and columns in B
      rows_A = len(A)
      cols_B = len(B[0])
      
      # Number of columns in A and rows in B (should be the same)
      cols_A = len(A[0])
      rows_B = len(B)
      
      # Initialize result matrix with zeros
      result = [[0 for _ in range(cols_B)] for _ in range(rows_A)]
      
      # Perform matrix multiplication
      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