'Returns True if \'self\' is a proper subset of \'other\'.
Examples
>>> from sympy import Interval
>>> Interval(0, 0.5).is_proper_subset(Interval(0, 1))
True
>>> Interval(0, 1).is_proper_subset(Interval(0, 1))
False'

def is_proper_subset(self, other):

    if isinstance(other, Set):
        return ((self != other) and self.is_subset(other))
    else:
        raise ValueError(("Unknown    argument    '%s'" % other))
