public void SelectRelationships( 
   IReadOnlyCollection<string> relationships
)

// get the active investigation view
var iv = KnowledgeGraphInvestigationView.Active;

// clear any TOC selection
iv.ClearTOCSelection();

// select entities
List<string> entities = new List<string>();
entities.Add("Person");
entities.Add("Org");
iv.SelectEntities(entities);

// or select relationships
List<string> relationships = new List<string>();
relationships.Add("HasEmployee");
iv.SelectRelationships(relationships);

// or select a combination
List<string> namedObjectTypes =  new List<string>();
namedObjectTypes.Add("Person");
namedObjectTypes.Add("Org");
namedObjectTypes.Add("HasEmployee");
iv.SelectNamedObjectTypes(namedObjectTypes);