input: Write a function to print characters in a string that are palindromes.
  assert print_palindromic_characters("I like mangoes") == ['I', ' ', ' ', ' ', 'e']
  assert print_palindromic_characters("racecar") == ['r', 'a', 'c', 'e', 'c', 'a', 'r']
  assert print_palindromic_characters("madam") == ['m', 'a', 'd', 'a', 'm']
output: def print_palindromic_characters(s):
      return [ch for ch in s if ch == ch[::-1]]