def remove(self, elem):
        """Remove a requirement.

        :param elem: a string or :class:`Requirement` instance.
        """
        if isinstance(elem, text_type):
            for requirement in self:
                if requirement.package == elem:
                    return super(Requirements, self).remove(requirement)
        return super(Requirements, self).remove(elem)
def on_upper_bound_changed(self):
        self.ui.spinBoxLowerBound.setMaximum(self.ui.spinBoxUpperBound.value() - 1)
        self.ui.spinBoxBoundaryNumber.setMaximum(math.ceil((self.ui.spinBoxUpperBound.value()
                                                            - self.ui.spinBoxLowerBound.value()) / 2))