Internal functions for drawing the pathway grob
# S3 method for biocarta_pathway_grob
makeContext(x)
# S3 method for biocarta_pathway_grob
grobWidth(x)
# S3 method for biocarta_pathway_grob
grobHeight(x)A grob returned by biocartaGrob().
makeContext() returns a grob object.
grobWidth() returns a unit object.
grobHeight() returns a unit object.