As a Wikidata reuser, I want to have a canonical URI for EntitySchemas in order to identify them as concepts and access them in various formats e.g. RDF.
**Problem:**
Although a URI scheme for EntitySchemas is being created in T225778, for it to be useful we will need to add the EntitySchema URIs in the RDF output of Items, Properties and Lexemes where EntitySchemas are addressed in the statements.
**BDD**
GIVEN an EntitySchema
AND an RDF export for an Item or Lexeme (once E Wikibase entitySchemas are able to be referenced in statements (Item, Lexeme etc.)
WHEN an EntitySchema is referenced in a statementthe value of a statement is an EntitySchema
THEN the referenceEntitySchema ID in the RDF output is a concept URIprefixed by `wd:`
**Acceptance criteria:**
[] A URI is used for an EntitySchema in an RDF export of an Item, Property or Lexeme that has that EntitySchema referenced in a statement
**Open questions:**The EntitySchema ID in the RDF output is prefixed by `wd:` when the value of a statement is an EntitySchema