How many {sidekick of} are to/by {Batman} ?
How many partners in crime does Batman work with?
How many sidekicks does the Batman have?
SELECT ( COUNT ( ?x ) AS ?e ) { ?x property:sidekick_of resource:Batman }
SELECT (COUNT(?sub) AS ?subs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> ?sub .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P2546> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q2695156 .
} 

SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P2546 wd:Q2695156 }
10