def square(x):
    """preconditon: x is a number
postcondtion: returns the square of the number passed it.
There are not side-effects"""
    return x*x
def greet_customer(name):
    """prec: name is a string
postcondition:  prints "Hello (name)." to the screen"""
    print(f"Hello, {name}")
def greet_customer1(name):
    """prec: name is a string
postcondition:  returns the string "Hello, (name)"""
    return f"Hello, {name}" 
print(square(10))
print(square.__doc__)
greet_customer("Shannon")
print(greet_customer1("Shannon"))