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\begin{alltt}
STk> (define g (graph)){\em{
\#[undefined]} }
\end{alltt}
\begin{alltt}
STk> (add-vertices! 1 4 g){\em{
\#[\(<\)set\(<\)vertex*\(>\)\(>\) \#p50c3dc]} }
\end{alltt}
\begin{alltt}
STk> (describe g){\em{
\#[\(<\)ubingraph*\(>\) \#p50c79c] is an instance of class \(<\)ubingraph*\(>\)
Slots are: 
     val = \{[1 2 3 4]  \{\}\}
\#f} }
\end{alltt}

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