[Biopython] gff3: feature.location.end problem

[Mic]

Hi,
When parsing this gff3 file:

##gff-version 3
##sequence-region ID1 1 20
ID1     prediction      gene    1       20      10.0    +       .
 other=Some,annotations;ID=gene1
ID1     prediction      exon    1       5       .       +       .
 Parent=gene1
ID1     prediction      exon    16      20      .       +       .
 Parent=gene1


with this code:

from BCBio import GFF  # handles GFF files

with open("test.gff3") as file:
    for rec in GFF.parse(file):
        annotations = rec.annotations['sequence-region'][0]
        id = annotations[0]
        start = int(annotations[1])
        end = int(annotations[2])
        print id, start, end

        for feature in rec.features:
            contig_id = feature.qualifiers['ID'][0]
            print contig_id, int(feature.location.start),
int(feature.location.end)

I get the following output:
ID1 1 20
gene1 0 20


Why is it not "gene1 0 19" and "ID1 0 19"?

Thank you in advance.

Mic