Write hierarchy below specfied GO IDs to an ASCII file.

def wrtxt_hier(self, fout_txt):
        """Write hierarchy below specfied GO IDs to an ASCII file."""
        with open(fout_txt, 'wb') as prt:
            self.prt_hier(prt)
            print("  WROTE: {TXT}".format(TXT=fout_txt))