input: Write a function in Python to create a random string of 10 characters. The function should generate a string of exactly 10 characters from a set of lowercase letters, uppercase letters, and digits. 
  
  
  def generate_random_string():
      random_characters = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'
      random_string = ''.join(random.choice(random_characters) for i in range(10))
      return random_string
  
  assert len(generate_random_string()) == 10
  assert any(char.islower() for char in generate_random_string()) == True
  assert any(char.isupper() for char in generate_random_string()) == True
  assert any(char.isdigit() for char in generate_random_string()) == True
  
output: import random
  
  def generate_random_string():
      random_characters = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'
      random_string = ''.join(random.choice(random_characters) for i in range(10))
      return random_string