(backport from rev. 53787)
format, write the packed bytes into the writable \var{buffer} starting at
\var{offset}.
Note that the offset is not an optional argument.
+
+ \versionadded{2.5}
\end{funcdesc}
\begin{funcdesc}{unpack}{fmt, string}
\var{buffer} must contain at least the amount of data required by the
format (\code{len(buffer[offset:])} must be at least
\code{calcsize(\var{fmt})}).
+
+ \versionadded{2.5}
\end{funcdesc}
\begin{funcdesc}{calcsize}{fmt}