Address the comment

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

@@ -217,7 +217,6 @@ message Const {
   oneof value {
     // This value should always be true if set, which represent the python None object.
     bool is_none = 1;
-
     float float_value = 2;
     int64 int_value = 3;
     string string_value = 4;

cirq-google/cirq_google/api/v2/sweeps.py

@@ -91,6 +91,8 @@ def sweep_to_proto(
             out.single_sweep.parameter.units = sweep.metadata.units
     elif isinstance(sweep, cirq.Points) and not isinstance(sweep.key, sympy.Expr):
         out.single_sweep.parameter_key = sweep.key
+        # Encoding the sinlge sweep with None to avoid the behavior modification.
+        # May remove the `sweep.points[0] is None` condition in future.
         if len(sweep.points) == 1 and sweep.points[0] is None:
             out.single_sweep.const.MergeFrom(_build_sweep_const(sweep.points[0]))
         else:

cirq-google/cirq_google/api/v2/sweeps_test.py

@@ -105,7 +105,7 @@ def test_sweep_to_proto_linspace():
 def test_build_recover_const(val):
     val2 = v2.sweeps._recover_sweep_const(v2.sweeps._build_sweep_const(val))
     if isinstance(val, float):
-        assert math.isclose(val, val2)
+        assert math.isclose(val, val2)  # avoid the floating precision issue.
     else:
         assert val2 == val