FIX: backslash escaped (#5815)

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LatexTextSplitter needs to use "\n\\\chapter" when separators are
escaped, such as "\n\\\chapter", otherwise it will report an error:
(re.error: bad escape \c at position 1 (line 2, column 1))


Fixes # (issue)

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re.error: bad escape \c at position 1 (line 2, column 1)

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Co-authored-by: Pang <ugfly@qq.com>

langchain/text_splitter.py

@@ -716,21 +716,21 @@ class RecursiveCharacterTextSplitter(TextSplitter):
         elif language == Language.LATEX:
             return [
                 # First, try to split along Latex sections
-                "\n\\chapter{",
-                "\n\\section{",
-                "\n\\subsection{",
-                "\n\\subsubsection{",
+                "\n\\\chapter{",
+                "\n\\\section{",
+                "\n\\\subsection{",
+                "\n\\\subsubsection{",
                 # Now split by environments
-                "\n\\begin{enumerate}",
-                "\n\\begin{itemize}",
-                "\n\\begin{description}",
-                "\n\\begin{list}",
-                "\n\\begin{quote}",
-                "\n\\begin{quotation}",
-                "\n\\begin{verse}",
-                "\n\\begin{verbatim}",
+                "\n\\\begin{enumerate}",
+                "\n\\\begin{itemize}",
+                "\n\\\begin{description}",
+                "\n\\\begin{list}",
+                "\n\\\begin{quote}",
+                "\n\\\begin{quotation}",
+                "\n\\\begin{verse}",
+                "\n\\\begin{verbatim}",
                 ## Now split by math environments
-                "\n\\begin{align}",
+                "\n\\\begin{align}",
                 "$$",
                 "$",
                 # Now split by the normal type of lines