null (nil) value
Some parameters support the null value. The descriptions of these parameters indicate “nillable”.
JSON
"_field_name_": null
SOAP
<_field_name_ xsi:nil="true">
Resetting (clearing) a parameter
In the update and set methods, you can pass null to delete the value for such a parameter.
Getting a parameter
If a parameter is requested but its value is not set, the get method returns null.