code: def get_random_letter(src_char=None):
      """
      Get replaced letter according src_char format.
  
      :param char src_char:
      :return: default return a lower letter
      """
  
      if src_char.isdigit():
          return random.choice(string.digits)
      if src_char.isupper():
          return random.choice(string.ascii_uppercase)
      else:
          return random.choice(string.ascii_lowercase)
  
imports: import random
  import string
label_desc: Use image node_id 2 for calling a global function with example usage: get_random_letter(src_char) and returns: random, random, random