gff to gtf file conversion

[Shukla04]

Hello
I simply used the gff3 to gtf conversion utility and ran into an error. Any help would be appreciated.

what i did
import bioinfokit
from bioinfokit.analys import gff
gff.gff_to_gtf(file="annotation.gff")

The error that follows is:
Traceback (most recent call last):
File "", line 1, in
File "/home/neha/anaconda3/lib/python3.9/site-packages/bioinfokit/analys.py", line 1340, in gff_to_gtf
cds_dict_st[transcript_id_cds].append(line[3])
KeyError: 'AT1G01010.1,AT1G01010.1-Protein'

Thanks