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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def tag(check, version, push, dry_run):
 """Tag the HEAD of the git repo with the current release number for a specific check. The tag is pushed to origin by default. You can tag everything at once by setting the check to `all`. Notice: specifying a different version than the one in __about__.py is a maintenance task that should be run under very specific circumstances (e.g. re-align an old release performed on the wrong commit). """

    tagging_all = check == 'all'

    valid_checks = get_valid_checks()
    if not tagging_all and check not in valid_checks:
        abort('Check `{}` is not an Agent-based Integration'.format(check))

    if tagging_all:
        if version:
            abort('You cannot tag every check with the same version')
        checks = sorted(valid_checks)
    else:
        checks = [check]

    # Check for any new tags
    tagged = False

    for check in checks:
        echo_info('{}:'.format(check))

        # get the current version
        if not version:
            version = get_version_string(check)

        # get the tag name
        release_tag = get_release_tag_string(check, version)
        echo_waiting('Tagging HEAD with {}... '.format(release_tag), indent=True, nl=False)

        if dry_run:
            version = None
            click.echo()
            continue

        result = git_tag(release_tag, push)

        if result.code == 128 or 'already exists' in result.stderr:
            echo_warning('already exists')
        elif result.code != 0:
            abort('\n{}{}'.format(result.stdout, result.stderr), code=result.code)
        else:
            tagged = True
            echo_success('success!')

        # Reset version
        version = None

    if not tagged:
        abort(code=2)