ArcGIS Pro 2.7 API Reference Guide
RulePackageAttribute Class
Members 

ArcGIS.Desktop.Mapping Namespace : RulePackageAttribute Class
Represents a rule package attribute and any associated annotations.
Syntax
public sealed class RulePackageAttribute 
Public NotInheritable Class RulePackageAttribute 
Remarks
A rule package attribute instance contains its name, value, and type along with a collection of any associated Annotations read from the City Engine rule file (please see below).
Note: CGA annotations can be referenced here:

Notes on Annotations:
@Angle, @Color, @Distance, @Percent
If present in the collection, they have no value @Hidden
Attributes annotated with @Hidden are not retrieved from the Rule Package.
@File and @Directory
Attributes annotated with @File or @Directory are not retrieved from the Rule Package. They are not supported for renderers. @Handle
@Handle is not retrieved. @In and @Out
@In and @Out are not retrieved. @In is reflected in the
RulePackageDescription.GeometryType. An @Out is implicitly always combinedShape. A value of separatedShapes for @Out is not supported. @Group with index
When an order index is added to a @Group ~that~ group order index is added as a GroupOrder key/value.
@Range
@Ranges can be numeric or a domain of specific values. Check the RangeType key. It will be one of "Range | Domain".
@StartRule
@StartRule is not retrieved.
Annotation keys:

Inheritance Hierarchy

System.Object
   ArcGIS.Desktop.Mapping.RulePackageAttribute

Requirements

Target Platforms: Windows 10, Windows 8.1

See Also

Reference

RulePackageAttribute Members
ArcGIS.Desktop.Mapping Namespace