input: Write a function to perform matrix multiplication on two given matrices. If the number of columns in the first matrix does not match the number of rows in the second matrix, raise a ValueError.
  
  def matrix_multiplication(A, B):  
      rows_A = len(A)  
      cols_A = len(A[0])  
      rows_B = len(B)  
      cols_B = len(B[0])  
      
      if cols_A != rows_B:
          raise ValueError("Number of columns in the first matrix must match the number of rows in the second matrix.")
      
      result = [[0 for i in range(cols_B)] for j 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
  
  assert matrix_multiplication([[1, 2], [3, 4]], [[1, 2], [3, 4]])==[[7, 10], [15, 22]]
  assert matrix_multiplication([[1, 2, 3], [4, 5, 6]], [[7, 8], [9, 10], [11, 12]])==[[58, 64], [139, 154]]
  try:
      matrix_multiplication([[1, 2], [3, 4]], [[1, 2, 3], [4, 5, 6]])
      assert False # This should not be executed
  except ValueError:
      assert True # This should be executed
  assert matrix_multiplication([], [])==[]
output: def matrix_multiplication(A, B):  
      rows_A = len(A)  
      cols_A = len(A[0]) if A else 0
      rows_B = len(B)  
      cols_B = len(B[0]) if B else 0
      
      if cols_A != rows_B:
          raise ValueError("Number of columns in the first matrix must match the number of rows in the second matrix.")
      
      result = [[0 for i in range(cols_B)] for j 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