Updated the use of None.

`if var == None` is equivalent to `if not var`
`if var != None` is equivalent to 'if var'

The if statement can check for existence.

Moreover,

While I do not know what `print_term` does, consider using the `__repr__` or `__str__` method instead. this way, it overloads the print operator so you can just use 

`str(Term_Object)`
`print(Term_Object)`