#7805

Fixed the bug by returning False when the method _contains of an Interval gets another Interval
Well, sometimes you can't evaluate that function with symbolic inputs:

In [6]: from sympy import Symbol, Interval

In [7]: x = Symbol('x')

In [8]: interval = Interval(0,1)

In [9]: x in interval
TypeError: proposition must be a valid logical expression

Should I leave it as it is?

concerning the case of isinstance, would this line cover all the cases we want to avoid?
if isinstance(other, Set):
    return False