Returns True if all chars in a string are upper case letters , otherwise rturns False
my_str='WELCOME TO PYTHON'
print(my_str.isupper()) # Output is True
my_str='Welcome to Python'
print(my_str.isupper()) # Output is False
my_str='Welcome To Python'
print(my_str.isupper()) # Output is False
my_str='WELCOME 100'
print(my_str.isupper()) # Output is True