def loads(self, requirements_text):
        lines = re.findall(Requirement.spec_regex,
                           requirements_text,
                           re.MULTILINE)
        for line in lines:
            self.add(Requirement(line[0], "".join(line[1:])))
def serialize(self, value, display=False):
        if value is True:
            return "true"
        elif value in (False, None):
            return "false"
        else:
            raise ValueError(f"{value!r} is not a boolean")