/usr/share/doc/seq-gen/examples/heterogeneity.tree is in seq-gen 1.3.4-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | [300, 0.482364](((Taxon1:0.2,Taxon2:0.2):0.1,Taxon3:0.3):0.1,Taxon4:0.4);
[400, 1.615264](((Taxon1:0.2,Taxon3:0.2):0.1,Taxon2:0.3):0.1,Taxon4:0.4);
[300, 0.697283](((Taxon1:0.2,Taxon2:0.2):0.1,Taxon3:0.3):0.1,Taxon4:0.4);
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