Return the current value of the Variable.

def value(self):
        """Return the current value of the Variable.
        """
        try:
            return self._value.value()
        except UnresolvedVariableValue:
            raise UnresolvedVariable("<unknown>", self)
        except InvalidLookupConcatenation as e:
            raise InvalidLookupCombination(e.lookup, e.lookups, self)