import string
def get_missing_alphabet_chars(input_str: str) -> list[str]:
# Normalize: lowercase + keep only letters
letters = [ch for ch in input_str.lower() if 'a' <= ch <= 'z']
# Unique letters present
present = set(letters)
# Alphabet minus present letters
missing = [ch for ch in string.ascii_lowercase if ch not in present]
return missing
missing = get_missing_alphabet_chars("Python Programming")
print(missing)
'''
run:
['b', 'c', 'd', 'e', 'f', 'j', 'k', 'l', 'q', 's', 'u', 'v', 'w', 'x', 'z']
'''