AFG3000: Use on_off_val_mapping instead of custom vals and get_parser

[mgunyho]

Before this change, setting boolean parameters to True/False failed silently:

from qcodes_contrib_drivers.drivers.Tektronix.AFG3000 import AFG3000

afg = AFG3000("AFG", address=...)

afg.state_output1.set(1)
assert afg.state_output1() is True  # ok

afg.state_output1.set(False)  # no error
assert afg.state_output1() is False  # fails, afg.state_output1 is still True !

# this works
afg.state_output1.set(0)
assert afg.state_output1() is False

With this patch, the second assert above also succeeds.

Note: while this is a bug in this driver, interestingly Enum(0, 1).validate(True) succeeds (works also with floats 0.0 and 1.0). Seems like this is due to hash(1) == hash(1.0) == hash(True) == 1. Perhaps this is a bit surprising, I would expect Enum to be a bit more strict. But maybe it's enough to warn about this in the documentation.

[codecov-commenter]

Codecov Report

Merging #131 (6cd28fd) into master (2fd9c39) will decrease coverage by 0.66%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #131      +/-   ##
==========================================
- Coverage   19.91%   19.24%   -0.67%     
==========================================
  Files         121      123       +2     
  Lines       14708    14629      -79     
==========================================
- Hits         2929     2816     -113     
- Misses      11779    11813      +34     

Impacted Files	Coverage Δ
...codes_contrib_drivers/drivers/Tektronix/AFG3000.py	0.00% <0.00%> (ø)
qcodes_contrib_drivers/__init__.py	100.00% <0.00%> (ø)
...es_contrib_drivers/drivers/CopperMountain/M5180.py	0.00% <0.00%> (ø)
...contrib_drivers/drivers/NationalInstruments/DAQ.py	0.00% <0.00%> (ø)
...contrib_drivers/drivers/Tektronix/Keithley_6500.py	0.00% <0.00%> (ø)
...ontrib_drivers/drivers/NationalInstruments/RFSG.py	0.00% <0.00%> (ø)
...ontrib_drivers/tests/QDevil/test_sim_qdac2_init.py	100.00% <0.00%> (ø)
...rib_drivers/tests/QDevil/test_sim_qdac2_current.py	100.00% <0.00%> (ø)
..._contrib_drivers/drivers/GeneralMicrowave/GM349.py	0.00% <0.00%> (ø)
...codes_contrib_drivers/drivers/Holzworth/HS9008B.py	0.00% <0.00%> (ø)
... and 2 more

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[astafan8]

@mgunyho

Note: while this is a bug in this driver, interestingly Enum(0, 1).validate(True) succeeds (works also with floats 0.0 and 1.0). Seems like this is due to hash(1) == hash(1.0) == hash(True) == 1. Perhaps this is a bit surprising, I would expect Enum to be a bit more strict. But maybe it's enough to warn about this in the documentation.

indeed :) i haven;t looked at it, but it might be related to the fact that in python True == 1 etc, as you also mention. so we can just keep it that.