Monophyly_prune errors with single species gene trees

[jasminelmah]

Monophyly_prune fails at line 80 sister = leaf.sister_nodes()[0] when encountering gene trees that have sequences from only a single species. The error:

Traceback (most recent call last):
File "/gpfs/ysm/project/dunn/jlm329/conda_envs/phylopytho/bin/treeprune", line 8, in
sys.exit(main())
File "/gpfs/ysm/project/dunn/jlm329/conda_envs/phylopytho/lib/python3.9/site-packages/phylopytho/treeprune.py", line 208, in main
tree = monophyly_prune(tree)
File "/gpfs/ysm/project/dunn/jlm329/conda_envs/phylopytho/lib/python3.9/site-packages/phylopytho/treeprune.py", line 80, in monophyly_prune
sister = leaf.sister_nodes()[0]
IndexError: list index out of range

An example of an offending tree:

(Schistosoma_mansoni@Smp-337900:0.00656752,((Schistosoma_mansoni@Smp-337890:0,Schistosoma_mansoni@Smp-337880:0):0.00126497,(((((Schistosoma_mansoni@Smp-318340:0.0369856,Schistosoma_mansoni@Smp-318350:0.00434441):0.233291,(Schistosoma_mansoni@Smp-337820:0.166968,Schistosoma_mansoni@Smp-332340:0.143222):0.122166):0.0392655,Schistosoma_mansoni@Smp-341850:0.508476):0.0292401,Schistosoma_mansoni@Smp-166690:0.627144):0.00657204,((((Schistosoma_mansoni@Smp-033380:0.526121,Schistosoma_mansoni@Smp-121230:0.599025):0.715415,Schistosoma_mansoni@Smp-166720:0.628339):0.0944244,(Schistosoma_mansoni@Smp-166730:0.0269917,Schistosoma_mansoni@Smp-337810:0.0366133):0.0844652):0.0173109,Schistosoma_mansoni@Smp-318370:0.0528969):0.196992):0.266284):0.00656752);