def freeze(h, output_yaml, resolve, groups):
    """Output installed packages."""
    if not groups:
        groups = filter(lambda group: not group.lower().startswith("bower"),
                        h.requirements.keys())
    else:
        groups = [text_type.strip(group) for group in groups.split(",")]

    if output_yaml:
        for requirements in h.requirements.values():
            for requirement in requirements:
                if resolve and not requirement.version:
                    requirement.load_installed_version()
        click.echo(h.requirements.yaml)
    else:
        for group in groups:
            if not h.requirements[group]:
                continue
            click.echo("# {}".format(group))
            for requirement in h.requirements[group]:
                if resolve and not requirement.version:
                    requirement.load_installed_version()
                click.echo(str(requirement))
def deadlines_for_courses(cls, course_keys):
        """
        Retrieve verification deadlines for particular courses.

        Arguments:
            course_keys (list): List of `CourseKey`s.

        Returns:
            dict: Map of course keys to datetimes (verification deadlines)

        """
        all_deadlines = cache.get(cls.ALL_DEADLINES_CACHE_KEY)
        if all_deadlines is None:
            all_deadlines = {
                deadline.course_key: deadline.deadline
                for deadline in VerificationDeadline.objects.all()
            }
            cache.set(cls.ALL_DEADLINES_CACHE_KEY, all_deadlines)

        return {
            course_key: all_deadlines[course_key]
            for course_key in course_keys
            if course_key in all_deadlines
        }