def add(self, elem, replace=False):
        """Add a requirement.

        :param elem: a string or :class:`Requirement` instance.
        :param replace: if `True`, packages in the set with the same name will
            be removed first.
        """
        if isinstance(elem, text_type):
            elem = Requirement.coerce(elem)
        if replace and elem in self:
            self.remove(elem)
        super(Requirements, self).add(elem)
def display(self, callingWindow, srcContext, mainItem):
        if srcContext not in ("marketItemGroup", "marketItemMisc") or self.mainFrame.getActiveFit() is None:
            return False

        if mainItem is None:
            return False

        for attr in ("emDamage", "thermalDamage", "explosiveDamage", "kineticDamage"):
            if mainItem.getAttribute(attr) is not None:
                return True

        return False