This API is subject to change. Bug fixes and new features will be released based on developer feedback throughout the preview period.
Refines a filter to match items whose specified field does not exist or does not have any value.
The isEmpty() method refines this filter to only match items where the
value of the specified field is null or undefined or the field does
not exist.
If the field contains any value at all for a given item, including the empty string or an invalid value, that item will match the filter.
Field in which to check for a value.