calculate field to null?

[DShokes]

I can't figure out the syntax for setting values to null.
I've tried:

fl.calculate(where="CustomerID=168453", calcExpression={"field" : "CompanyName_1", "value" : null})
fl.calculate(where="CustomerID=168453", calcExpression={"field" : "CompanyName_1", "value" : NULL})
fl.calculate(where="CustomerID=168453", calcExpression={"field" : "CompanyName_1", "value" : <Null>})
#all errors as expected

fl.calculate(where="CustomerID=168453", calcExpression={"field" : "CompanyName_1", "value" : 'null'})
fl.calculate(where="CustomerID=168453", calcExpression={"field" : "CompanyName_1", "value" : '<Null>'})
#return string values

fl.calculate(where="CustomerID=168453", calcExpression={"field" : "CompanyName_1", "value" : None})
# {'error': {'message': 'Unable to calculate fields.', 'code': 400, 'details': ['Object reference not set to an instance of an object.']}}

Thanks

[DShokes]

I think I solved it.

fl.calculate(where="CustomerID=168453", calcExpression={"field" : "CompanyName_1", "sqlExpression" : "null"}, sqlFormat="native") )

Perhaps arcREST would benefit with a sample using calculate variations of "value" and "sqlExpression" with sqlFormat="native" or "standard"

I'm still having issues calculating a value with single quotes:

fl.calculate(where="CustomerID=168453", calcExpression={"field" : "CompanyName_1", "sqlExpression" : "Applebee's"}, sqlFormat="native") )

but this may be unrelated to arcREST.