Allow passing a callable to de/serialization funcs

[senecameeks]

This gives us flexibility to manipulate the cirq.Sweep to add units for example.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.85%. Comparing base (2448121) to head (8cb0db8).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6855      +/-   ##
==========================================
- Coverage   97.86%   97.85%   -0.01%     
==========================================
  Files        1084     1084              
  Lines       93954    94013      +59     
==========================================
+ Hits        91944    91997      +53     
- Misses       2010     2016       +6     

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[pavoljuhas]

Perhaps I am missing something, but I am not sure why is this needed.
The main code seems to be handling Linspace with units just fine,
so why is it necessary to support conversion of plain Linspace to Linspace with-units inside sweep_to_proto with a special callable?

import cirq
import tunits
from cirq_google.api import v2

sweep = cirq.Linspace('foo', 3 * tunits.ns, 6 * tunits.ns, 3)
print(sweep)
msg = v2.sweep_to_proto(sweep)
sweep_rt = v2.sweep_from_proto(msg)
print(sweep_rt)

[NoureldinYosri]

@senecameeks Great idea Seneca! ... just a few changes

---

@pavoljuhas this is to allow serialization of sweeps that use the internal units library ... otherwise we will need to replicate the logic in these functions internally.

[senecameeks]

Echoing what Nour said, this ability is needed to support serialization of the internal unit library @pavoljuhas

[BichengYing]

lgtm

[BichengYing]

note in cirq, we have cirq.SingleSweep (the parent class of cirq.Points and cirq.Linspace).

So it can be more precise with
single_sweep_transformer: Callable[[cirq.SingleSweep], cirq.SingleSweep]

[NoureldinYosri]

@senecameeks for typing you can do this

_SWEEP_T = TypeVar('_SWEEP_T', cirq.Points, cirq.Linspace)  # or just cirq.SingleSweep

Callable[[_SWEEP_T], _SWEEP_T]

this will remove the cast statements below

[senecameeks]

this still causes mypy to fail, but also I prefer using cirq.SingleSweep in the call over type vars since IMO the former is more readable. So I'll keep as is

[NoureldinYosri]

the TypeVar tells mypy that the type of the output is the same as the type of the input e.g. if input is Linspace mypy will expect the output to also be Linspace

[BichengYing]

can you add another test that add tunit in sweep_to_proto while remove tunit in sweep_from_proto, this is a more practical usage in the pyle.

[senecameeks]

Done

[BichengYing]

@NoureldinYosri why it is tunits.Value unit instead of tunits.Unit unit here? Is that because of multiple combinations of units and we just ignore the value here?

Cirq/cirq-google/cirq_google/api/v2/run_context.proto

Lines 210 to 215 in 2448121

	message Points {
	// The values.
	repeated float points = 1;
	tunits.Value unit = 2;
	}

[NoureldinYosri]

@NoureldinYosri why it is tunits.Value unit instead of tunits.Unit unit here? Is that because of multiple combinations of units and we just ignore the value here?

Cirq/cirq-google/cirq_google/api/v2/run_context.proto

Lines 210 to 215 in 2448121

	message Points {
	// The values.
	repeated float points = 1;
	tunits.Value unit = 2;
	}

@BichengYing tunits doesn't have a Unit in the public api ... for performance units are implemented in the cython layer as essnetially arrays ... the public api of tunits has only Value, ValueArray and their subclasses

[NoureldinYosri]

LGTM%typing nit & other reviewers' comments

[NoureldinYosri]

@senecameeks for typing you can do this

_SWEEP_T = TypeVar('_SWEEP_T', cirq.Points, cirq.Linspace)  # or just cirq.SingleSweep

Callable[[_SWEEP_T], _SWEEP_T]

this will remove the cast statements below