GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it
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#W treeaut.gd automgrp package Yevgen Muntyan
#W Dmytro Savchuk
## automgrp v 1.3
##
#Y Copyright (C) 2003 - 2016 Yevgen Muntyan, Dmytro Savchuk
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#C IsTreeAutomorphism
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## Category of rooted tree automorphisms.
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DeclareCategory("IsTreeAutomorphism", IsTreeHomomorphism and
IsMultiplicativeElementWithInverse);
DeclareCategoryFamily("IsTreeAutomorphism");
DeclareCategoryCollections("IsTreeAutomorphism");
InstallTrueMethod(IsActingOnTree, IsTreeAutomorphismFamily);
InstallTrueMethod(IsActingOnTree, IsTreeAutomorphismCollection);
InstallTrueMethod(IsGeneratorsOfMagmaWithInverses, IsTreeAutomorphismCollection);
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#O TreeAutomorphism( <states>, <perm> )
##
## Constructs the tree automorphism with states on the first level given by the
## argument <states> and acting
## on the first level as the permutation <perm>. The <states> must
## belong to the same family.
## \beginexample
## gap> L := AutomatonGroup("p=(p,q)(1,2), q=(p,q)");
## < p, q >
## gap> r := TreeAutomorphism([p, q, p, q^2],(1,2)(3,4));
## (p, q, p, q^2)(1,2)(3,4)
## gap> t := TreeAutomorphism([q, 1, p*q, q],(1,2));
## (q, 1, p*q, q)(1,2)
## gap> r*t;
## (p, q^2, p*q, q^2*p*q)(3,4)
## \endexample
##
DeclareOperation("TreeAutomorphism", [IsList, IsPerm]);
DeclareOperation("TreeAutomorphismFamily", [IsObject]);
DeclareOperation("TreeAutomorphism", [IsObject, IsObject, IsPerm]);
DeclareOperation("TreeAutomorphism", [IsObject, IsObject, IsObject, IsPerm]);
DeclareOperation("TreeAutomorphism", [IsObject, IsObject, IsObject, IsObject, IsPerm]);
DeclareOperation("TreeAutomorphism", [IsObject, IsObject, IsObject, IsObject, IsObject, IsPerm]);
#E