input: Write a function to generate a random string of a specified length using a combination of alphanumeric characters (both uppercase and lowercase) and digits. The function should take an integer parameter representing the desired length of the string and return the randomly generated string.
  
  def generate_string(string_length):
      random_characters = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'
      random_string = ''.join(random.choices(random_characters, k=string_length))
      return random_string
  
  print(generate_string(10)) # Length: 10
  print(generate_string(20)) # Length: 20
  print(generate_string(0)) # Length: 0
output: import random
  
  def generate_string(string_length):
      random_characters = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'
      random_string = ''.join(random.choices(random_characters, k=string_length))
      return random_string