Adding annotations to a pdf

Dear all,

using reportlab in python, I manged to print a text and export this to a 
new pdf:
canvas.drawString(10, 100, "Hello world")

However, I didn't manage to add an annotation. I tried

canvas.highlightAnnotation("TEST", Rect=[1, 1, 1, 1], relative=1)

which didn't raise an error, however evince cannot parse the resulting 
pdf file.
Am I doing something wrong? The docu of the related functions is very 
sparse, so I would appreciate any help.

Cheers!