input: 
  import random
  
  def generate_string(string_length):
      """Generate a random string of given length.
      >>> generate_string(10)
      'A1b2C3d4E5'
      >>> generate_string(5)
      'aBcDe'
      """
      random_characters = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'
      random_string = ''.join(random.choices(random_characters, k=string_length))
      return random_string
  
output:     return random_string