Return true if the x is a recognised actor type, else false.

Quick function to replace the pattern (nil-if-empty (remove nil? (concat …))) which I’m using a lot!

Returns true iff x quacks like an ActivityStreams context, else false.

A context is either 1. the URI (actually an IRI) activitystreams-context-uri, or 2. a collection comprising that URI and a map.

Return a list of reports taken from these reports where the severity of the report is greater than this or equal to this severity.

Return true if the object x has a type which is an activity type, else false.

Return true if the object x has a type which is an actor type, else false.

True if x is an ActivityStreams object with a valid context, else false.

If object x has a :type value which is acceptable, return nil; else return a fault object with this severity and token.

acceptable may be passed as either nil, a string, or a set of strings. If acceptable is nil, no type specific tests will be performed.

Return true if object x has type type, else false.

The values of type fields of ActivityStreams objects may be lists; they are considered to have a type if the type token is a member of the list.

Return a fault object with these severity, fault and narrative values.

An ActivityPub object MUST have a globally unique ID. Whether this is meaningful depends on whether we persist fault report objects and serve them, which at present I have no plans to do.

if x is an empty collection, return nil; else return x.

Return true if x is truthy, else false.

true if x, a string, represents a recognised ActivityStreams activity type.