Writing saving generated gtf class object

[BrunoGuillotin]

Hi,
Thanks for creating this super simple tool to open and modify gtfs. I used it to add the introns not annotated in my gtf (from Zea mays aka corn). Worked like a charm.

gtf_file <- file.path("Zea_mays.B73_RefGen_v4.47.gtf")
gtf <- read_format(gtf_file)
update gtf with intron coordinates from the exon gaps
and return the updated object
ans <- construct_introns(gtf, update=TRUE)[]default
same as above, but returns only constructed introns
introns <- construct_introns(gtf, update=FALSE)

But how do I save the generated gtf (introns and ans) ?
I would like to use it with bedtools but every ways i tried to save the gtf object give me a file with an excessive amount of column that is not recognise as a gtf.

Thanks in advance for your great help,
B.