Hello,
I get an error "'GpibInstrument' object has no attribute 'write_raw'" with following code from your example:
import ivi
from ivi.agilent.agilentE3649A import agilentE3649A
inst = ivi.agilent.agilentE3649A("GPIB0::5::INSTR")
I use NI GPIB-USB-HS adaptor.
Regards