有人知道如何解决这个警告吗？
文档由多个章节组成，通过 \input 命令包含。该警告不会影响文档的编译过程（至少目前不会）。
序言如下：
\documentclass[a4paper, twoside, 12pt]{report}
\usepackage[letterpaper, left=2.9cm, right=2.9cm, top=2.5cm, bottom=2.5cm]{geometry}
\usepackage[spanish]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{hyperref}
\hypersetup{colorlinks=true, urlcolor=violet, linkcolor=Blue, citecolor=Sepia}
\usepackage{graphicx}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage[tight,footnotesize]{subfigure}
\renewcommand{\figurename}{Figura}
\renewcommand{\tablename}{Tabla}
\usepackage{pifont}
\usepackage{enumerate}
\usepackage[usenames,dvipsnames,svgnames,table]{xcolor}
\usepackage[square,sort,comma,numbers]{natbib}
\usepackage{tcolorbox}
\newtcolorbox{mybox}{colback=green!3,colframe=green!75!black}
\newtcolorbox{mybox2}{,colback=blue!3!white,colframe=blue!75!black}
\usepackage{multirow}
\usepackage{cancel}
\renewcommand{\theenumi}{\Roman{enumi}}
\usepackage[version=4]{mhchem}
\usepackage{tabularx}
\usepackage{supertabular}
\setlength{\parskip}{5mm}
%\setlength{\parindent}{0cm}
\usepackage{fancyhdr}
\pagestyle{fancy}
\usepackage{appendix}
\newtcolorbox[auto counter, number within=section]{example}[2][]
{colback=green!5!white,colframe=green!75!black,
fonttitle=\bfseries, title=Ejemplo~\thetcbcounter: #2,#1}
\usepackage{wrapfig} % Colocar figuras al lado del texto
\usepackage{float}
\usepackage{titlesec, blindtext, color}
\definecolor{gray75}{gray}{0.75}
\newcommand{\hsp}{\hspace{20pt}}
\titleformat{\chapter}[hang]{\Huge\bfseries}{\thechapter\hsp\textcolor{gray75}{|}\hsp}{0pt}{\Huge\bfseries}
\usepackage{epigraph}