c# validation nullable value

Hi,
We have a swagger spec with a value that is conditional/optional i.e. can be null with some validation constraints ("multipleOf": 0.001) this is presented like so:
```
"totalThroughputMibps": {
"type": "number",
"x-nullable": true,
"description": "Total throughput of pool in Mibps",
"example": 164.221,
"readOnly": true,
"multipleOf": 0.001
}
```

This causes issues with c# generated SDK where the validation code does not allow null values.

```
public double? TotalThroughputMibps { get; private set; }
.
.
.
.
.
if (TotalThroughputMibps % 0.001 != 0)
{
throw new ValidationException(ValidationRules.MultipleOf, "TotalThroughputMibps", 0.001);
}
```

Is it possible to present this in the swagger so that the validation in the generated code handles null values correctly?

ps I asked this in autorest repo as well but not getting any response there
https://github.com/Azure/autorest/issues/3585