def to_full_html_document(html_template_chunk: str) -> str:
    """
    Convert a HTML chunk into a full, valid html document.
    """
    result = ""
    result += "<!DOCTYPE html>\n"
    result += "<html>\n"
    result += "<body>\n"
    result += html_template_chunk + '\n'
    result += "</body>\n"
    result += "</html>\n"

    return result