Помогите разобраться с заданием:
Check if a given string has all symbols in upper case. If the string is empty or doesn't have any letter in it - function should return True.
Input: A string.
Output: a boolean.
Example:
is_all_upper('ALL UPPER') == True
is_all_upper('all lower') == False
is_all_upper('mixed UPPER and lower') == False
is_all_upper(") == True
is_all_upper('444') == True
is_all_upper('55 55 5') == True