Creating double arrow / parallel arrows with pb-diagram [duplicate]

I made this diagram and the only thing I want are two parallel arrows that go from node A to B and vice versa by using pb-diagram package, so that I can label both arrows differently, because both nodes interact.

• Welcome to TeX.SE! Please post the code that generates the graph that you show. This will make it a lot easier to help you. Just add the code (from \documentclass to \end{document}) to you posting. Mar 5 '17 at 10:21

A possibile solution using tikz-cd.

\documentclass[a4paper,12pt]{article}
\usepackage{amsmath}
\usepackage{tikz-cd}
\newcommand*\circlett[1]{%
\begin{tikzpicture}
\node[draw,circle,inner sep=.5pt] {#1};
\end{tikzpicture}}

\begin{document}
\begin{tikzcd}[row sep=4cm, column sep=2cm]
& \circlett{A} \arrow[ld,Leftrightarrow, "\mathrm{A-B}", "\mathrm{B-A}"'] & \\
\circlett{B}\arrow[rr,leftrightarrow, "\mathrm{B-C}", "\mathrm{C-B}"'] & & \circlett{C} \arrow[lu,Leftrightarrow, "\mathrm{C-A}", "\mathrm{A-C}"']
\end{tikzcd}

\end{document}