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 addOperators(self, num, target):
        """
        Adapted from https://leetcode.com/discuss/58614/java-standard-backtrace-ac-solutoin-short-and-clear

        Algorithm:
        1. DFS
        2. Special handling for multiplication
        3. Detect invalid number with leading 0's
        :type num: str
        :type target: int
        :rtype: List[str]
        """
        ret = []
        self.dfs(num, target, 0, "", 0, 0, ret)
        return ret