BUG: taxonomy.getAncestry('taxid') does not redirect old taxid to new node with pruned taxonomy

[AndrazMarinc]

First, thank you for this great toolkit, it's super convenient.

I think I might be dealing with a bug.
Version used: 3.1.1

Steps to reproduce:

1. download taxdump
2. Run code:

import taxidTools as txd

TAXDUMP = 'path_to_taxdump/'

tax = txd.read_taxdump(
    f'{TAXDUMP}nodes.dmp',
    f'{TAXDUMP}rankedlineage.dmp',
    f'{TAXDUMP}merged.dmp'
)

# Prune to only keep embryophyta to avoid ambiguity.
tax_pruned = tax.copy() 
tax_pruned.prune(3193)

# Get ancestry of "Liliaceae" from pruned taxonomy. Throws an error. 
tax_id_pruned = tax_pruned.getTaxid('Liliaceae')
tax_pruned.getAncestry(tax_id_pruned)  # Throws an error.

# Get ancestry of "Liliaceae" from original taxonomy. Works fine.
tax_id = tax.getTaxid('Liliaceae')
tax.getAncestry(tax_id)   # Works fine.

#  Both taxonomy ids are the same.
tax_id == tax_id_pruned