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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _get_taxon(taxon):
 """Return Interacting taxon ID | optional | 0 or 1 | gaf column 13."""

        if not taxon:
            return None
        ## assert taxon[:6] == 'taxon:', 'UNRECOGNIZED Taxon({Taxon})'.format(Taxon=taxon)
        ## taxid = taxon[6:]
        ## assert taxon[:10] == 'NCBITaxon:', 'UNRECOGNIZED Taxon({Taxon})'.format(Taxon=taxon)
        ## taxid = taxon[10:]
        # Get tzxon number: taxon:9606 NCBITaxon:9606
        sep = taxon.find(':')
        taxid = taxon[sep + 1:]
        assert taxid.isdigit(), "UNEXPECTED TAXON({T})".format(T=taxid)
        return int(taxid)