How to add a title and note to this table?

I am trying to add a title and a note to the following table:

\documentclass{article}\usepackage{longtable,pdflscape}\begin{document}\begin{longtable}[{l*{6}{c}r}]    \hline & Gov. Rev & Gov. Exp & Interest Rate & DFPA & GDP & Inflation \\     \hline \endhead    \textit{Business Cycle shock} & +&  & & & +& + \\    \textit{Monetary Policy shock}  &  & & $-$ & & +& + \\    \textit{DFPA shock}      & +& $-$ & & $-$ & &  \\\end{longtable}\end{document}

This is my attempt:

\documentclass{article}\usepackage{booktabs, caption}\usepackage{float}\usepackage[flushleft]{threeparttable}\begin{document}\begin{longtable}[{l*{6}{c}r}]\centering\begin{threeparttable}\caption{Identifying Sign Restrictions}    \hline & Gov. Rev & Gov. Exp & Interest Rate & DFPA & GDP & Inflation \\     \hline \endhead    \textit{Business Cycle shock} & +&  & & & +& + \\    \textit{Monetary Policy shock}  &  & & $-$ & & +& + \\    \textit{DFPA shock}      & +& $-$ & & $-$ & &  \\\begin{tablenotes}\small\item \textit{Note}: This table shows the sign restrictions on the impulse responses for each identified shock. A \enquote{$+$} means that the impulse response of the variable in question is restricted to be positive for six months following the shock, including the month of impact. Likewise, a \enquote{$-$} indicates a negative response. A blank entry indicates that no restrictions have been imposed.\end{tablenotes}\end{threeparttable}    \end{longtable}\end{document}

This, however, fails to deliver what I would like to get. Besides, I would like the table to be centred.

Can anyone help me?

Thanks a lot!