AQL: collection not known to traversal: "dataSource"

[wajda]

WITH executionPlan, executes, operation
FOR ep IN executionPlan
    FILTER ep._key IN @keys

    LET wo = FIRST(FOR v IN 1 OUTBOUND ep executes RETURN v)
    LET ds = FIRST(FOR v IN 1 OUTBOUND ep affects RETURN v)

    RETURN {
        "executionPlanKey" : ep._key,
        "frameworkName"    : CONCAT(ep.systemInfo.name, " ", ep.systemInfo.version),
        "applicationName"  : ep.name,
        "dataSourceUri"    : ds.uri,
        "dataSourceName"   : ds.name,
        "dataSourceType"   : wo.extra.destinationType,
        "append"           : wo.append
    }