formatting - capabilities.json

The following formatting gives me this error - gets the following error error JSON capabilities.json : instance.dataViewMappings[0] is not exactly one from [subschema 0],[subschema 1],[subschema 2],[subschema 3],[subschema 4]

{ "dataRoles": [ { "displayName": "dbId", "name": "dbid", "kind": "Grouping" }, { "displayName": "URN", "name": "urn", "kind": "Measure" } ], "dataViewMappings": [ { "table": { "rows": { "for": { "in": "dbid" } } }, "single": { "role": "urn" } } ] }

Im sure it is a basic formatting issue but I can’t figure it out, would someone be able to advise ?

Thanks Tom