Hello, I'm very new to using R and Bioconductor and I'm having some trouble converting a txdb file to a GRanges file. I have installed the GenomicRanges package. I think GenomicRanges has installed correctly as I get other options for this package but cannot seem to access 'toGRanges'

annotation_file <- toGRanges(txdb, feature="gene")

My output is then:

Error in toGRanges(txdb, feature = "gene") : 
  could not find function "toGRanges"

I am currently using RStudio Version 1.4.1717. Any help would be greatly appreciated!

This function is not part of the Grangespackage but the ChIPpeakAnno package : https://www.rdocumentation.org/packages/ChIPpeakAnno/versions/3.6.5/topics/toGRanges