Minor style nit for referring to other attributes of the same class

from an attributes description.

Doc/lib/emailmessage.tex

@@ -39,7 +39,7 @@ returned string.  \var{unixfrom} defaults to \code{False}.
 \end{methoddesc}
 
 \begin{methoddesc}[Message]{__str__}{}
-Equivalent to \method{aMessage.as_string(unixfrom=True)}.
+Equivalent to \method{as_string(unixfrom=True)}.
 \end{methoddesc}
 
 \begin{methoddesc}[Message]{is_multipart}{}