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 _handle_sigint_if_enabled(self, signum, _frame):
        with self._ignore_sigint_lock:
            self._check_sigint_gate_is_correct()
            threads_ignoring_sigint = self._threads_ignoring_sigint
            ignoring_sigint_v2_engine = self._ignoring_sigint_v2_engine
        if threads_ignoring_sigint == 0 and not ignoring_sigint_v2_engine:
            self.handle_sigint(signum, _frame)