Moved __contains__ to the sequence module, providing an implementation.
Added tests of "in", "not in" and operator syntax.
1deff(x): 2defg(y,x=x): 3while1: 4defh(z,x=x,y=y): 5returnx,y,z,a 6a=4# not available for h, available in Python 7returnh 8returng 9 10result=f(1)(2)(3) 11assertresult==(1,2,3,4)