input: Write a python function to generate a 3x3 matrix with random integers between 1 and 5 using numpy.
  assert random_matrix().shape == (3, 3)
  assert random_matrix().max() <= 5
  assert random_matrix().min() >= 1
output: import numpy as np
  
  def random_matrix():
      return np.random.randint(1, 6, size=(3, 3))