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 current_label(self) -> ProtocolLabel:
        if len(self.message.message_type) == 0:
            return None

        cur_label = self.message.message_type[self.current_label_index].get_copy()
        self.message.message_type[self.current_label_index] = cur_label
        cur_label.fuzz_values = [fv for fv in cur_label.fuzz_values if fv]  # Remove empty strings

        if len(cur_label.fuzz_values) == 0:
            cur_label.fuzz_values.append(self.message.plain_bits_str[cur_label.start:cur_label.end])
        return cur_label