def coerce(cls, string):
        """Create a :class:`Requirement` object from a given package spec."""
        match = re.match(cls.spec_regex, string)
        if not match:
            raise InvalidRequirementSpecError("could not parse requirement")
        package = match.group(1)
        if all(match.group(2, 3)):
            version = "".join(match.group(2, 3))
        else:
            version = None
        return cls(package, version)
def delete_lines(self, min_row, max_row):
        if min_row == -1:
            self.current_label.fuzz_values = self.current_label.fuzz_values[:-1]
        else:
            self.current_label.fuzz_values = self.current_label.fuzz_values[:min_row] + self.current_label.fuzz_values[
                                                                                        max_row + 1:]

        _ = self.current_label  # if user deleted all, this will restore a fuzz value

        self.fuzz_table_model.update()