This method is used to retrieve a property of the interaction. Properties
of all interactions are: interaction_id, type, client_ip, and time_stamp.
Properties of DNS interactions are: query_type and raw_query. The
raw_query value is Base64-encoded. Properties of HTTP interactions are:
protocol, request, and response. The request and response values are
name - The name of the property to retrieve.
A string representing the property value, or null if not present.