def extractContent(completeDocument):
    """The method takes a string representing a LaTeX document and separates its preamble (the portion before "\\begin{document}"), its content and its epilogue (after \\end{document}) and returns them in a list.
        Args:
            completeDocument(str): The LaTeX document as a string.
        Returns:
            list[str,str,str]: A list of three strings, the first one the portion before \\begin{document}(inclusive), the second one the document, the last one the part after \\end{document}."""
    preamble = ''
    document = ''
    epilogue = ''
    try:
        preamble = completeDocument[:completeDocument.index(
            '\\begin{document}')]
        document = completeDocument[completeDocument.index(
            '\\begin{document}'):completeDocument.index('\\end{document}') +
            len('\\end{document}')]
        epilogue = completeDocument[completeDocument.index(
            '\\end{document}') + len('\\end{document}'):]
    except ValueError:
        print('\\begin{document} or \\end{document} not found.\n')
    return [preamble, document, epilogue]
