input: Write a python function to generate a random integer between a given range.
  assert isinstance(random_integer(1, 10), int)
  assert 1 <= random_integer(1, 10) <= 10
  assert 50 <= random_integer(50, 100) <= 100
output: import random
  
  def random_integer(start, end):
      return random.randint(start, end)