def indent(lines_str, indent_size=2):
    """
    Indent a multi-line string with a common indent.

    :param lines_str: Multi-line string.
    :type lines_str: ``str``
    :param indent_size: Number of spaces to indent by - defaults to 2.
    :type indent_size: ``int``
    :return: New string with extra indent.
    :rtype: ``str``
    """
    indent = " " * indent_size
    return "\n".join(
        "{indent}{line}".format(indent=indent, line=line)
        for line in lines_str.splitlines()
    )