GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
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## SimplicialSet.gd SCO package Simon Goertzen
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## Copyright 2007-2008 Lehrstuhl B für Mathematik, RWTH Aachen
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## Declaration stuff for SCO.
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DeclareCategory( "IsSimplicialSet",
IsAttributeStoringRep );
DeclareOperation( "SimplicialSet",
[ IsOrbifoldTriangulation ] );
DeclareOperation( "SimplicialSet",
[ IsSimplicialSet, IsInt ] );
DeclareOperation( "ComputeNextDimension",
[ IsSimplicialSet ] );
DeclareOperation( "Extend",
[ IsSimplicialSet, IsInt ] );