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 prompt_subreddit(self):
        "Open a prompt to navigate to a different subreddit"

        name = self.term.prompt_input('Enter page: /')
        if name is not None:
            with self.term.loader('Loading page'):
                content = SubredditContent.from_name(
                    self.reddit, name, self.term.loader)
            if not self.term.loader.exception:
                self.selected_subreddit = content
                self.active = False