def indented(contentstring, indent=-1):
    """
    Return indented content.
    indent >= 0 prefixes content with newline + 2 * indent spaces.
    indent < 0 returns content unchanged

    Docstrings:
    >>> indented("foo bar", -1)
    'foo bar'

    >>> indented("foo bar", 0)
    '\\nfoo bar'

    >>> indented("foo bar", 1)
    '\\n  foo bar'

    """
    if not indent >= 0:
        return contentstring
    else:
        return "\n{}{}".format("  " * indent, contentstring)