def headers_raw_to_dict(headers_raw):
    """
    Convert raw headers (single multi-line string)
    to the dictionary.

    For example:
    >>> headers_raw_to_dict("Content-type: text/html\\n\\rAccept: gzip\\n\\n")
    {'Content-type': ['text/html'], 'Accept': ['gzip']}

    Incorrect input:
    >>> headers_raw_to_dict("Content-typt gzip\\n\\n")
    {}

    Argument is None:
    >>> headers_raw_to_dict(None)
    """
    if headers_raw is None:
        return None
    return dict([
        (header_item[0].strip(), [header_item[1].strip()])
        for header_item
        in [
            header.split(':', 1)
            for header
            in headers_raw.splitlines()]
        if len(header_item) == 2])