input: Write a function to generate a random string of a specified length using alphanumeric characters.
  
  def generate_string(string_length):
      random_characters = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'
      random_string = ''.join(random.choices(random_characters, k=string_length))
      return random_string
  
  assert generate_string(5) != generate_string(5)
  assert len(generate_string(10)) == 10
  assert any(char.isdigit() for char in generate_string(10))
  assert any(char.islower() for char in generate_string(10))
  assert any(char.isupper() for char in generate_string(10))
output: def generate_string(string_length):
      random_characters = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'
      random_string = ''.join(random.choices(random_characters, k=string_length))
      return random_string