\begin{flushleft}
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\begin{alltt}
STk> (define vs (vertices g)){\em{
\#[undefined]} }
\end{alltt}
\begin{alltt}
STk> (describe vs){\em{
\#[\(<\)set\(<\)vertex*\(>\)\(>\) \#p4f5798] is an instance of class \(<\)set\(<\)vertex*\(>\)\(>\)
Slots are: 
     val = \{1 2 3 4\}
\#f} }
\end{alltt}
\begin{alltt}
STk> (define es (choose vs 2)){\em{
\#[undefined]} }
\end{alltt}
\begin{alltt}
STk> (describe es){\em{
\#[\(<\)set\(<\)set\(<\)vertex*\(>\)\(>\)\(>\) \#p4e5598] is an instance of class \(<\)set\(<\)set\(<\)vertex*\(>\)\(>\)\(>\)
Slots are: 
     val = \{\{1 2\} \{1 3\} \{1 4\} \{2 3\} \{2 4\} \{3 4\}\}
\#f} }
\end{alltt}

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