'Return the Python type object expected to be returned
by instances of this type, if known.
Basically, for those types which enforce a return type,
or are known across the board to do such for all common
DBAPIs (like ``int`` for example), will return that type.
If a return type is not defined, raises
``NotImplementedError``.
Note that any type also accommodates NULL in SQL which
means you can also get back ``None`` from any type
in practice.'

@property
def python_type(self):

    raise NotImplementedError()
