Remove uniform indents from ``doc`` lines that are not empty

    :returns: Cleaned ``doc``

def _cleandoc(doc):
    """Remove uniform indents from ``doc`` lines that are not empty

    :returns: Cleaned ``doc``
    """
    indent_length = lambda s: len(s) - len(s.lstrip(" "))
    not_empty = lambda s: s != ""

    lines = doc.split("\n")
    indent = min(map(indent_length, filter(not_empty, lines)))

    return "\n".join(s[indent:] for s in lines)