FHIR R4 and Open.Epic FHIR Sandbox Mapping

FHIR R4 Encounter Resource has fields – basedOn and ServiceProvider (highlighted in the screenshot below), through which we can get the performing Encounter and Organization details. I am looking for these fields in Open Epic Sandbox but couldn’t find them. Do you have any suggestions to get these details from Epic Sandbox?

Epic-specific questions are best raised to open@epic.com

They said that DiagnosticReport is an answer but it isn’t quite right. Hence, reaching out to the forum here.