input: Write a function to generate a Python program to perform matrix multiplication on two given matrices. If the given matrices cannot be multiplied, return an error message.
  
  assert matrix_multiplication([[1, 2], [3, 4]], [[5, 6], [7, 8]]) == [[19, 22], [43, 50]]
  assert matrix_multiplication([[1, 2, 3], [4, 5, 6]], [[7, 8], [9, 10], [11, 12]]) == [[58, 64], [139, 154]]
  assert matrix_multiplication([[1, 2]], [[3], [4]]) == [[11]]
output: def matrix_multiplication(A, B):
      if len(A[0]) != len(B):
          return "Error: Matrices cannot be multiplied"
      result = [[0 for _ in range(len(B[0]))] for _ in range(len(A))]
      for i in range(len(A)):
          for j in range(len(B[0])):
              for k in range(len(B)):
                  result[i][j] += A[i][k] * B[k][j]
      return result