http://hl7.org/fhir/StructureDefinition/operationdefinition-allowed-type|4.0.1

When the base type is an abstract type (e.g. Resource or Element) then this extension defines which concrete types are allowed to be used for a parameter. In the absence of this extension, any type is allowed.
Base: http://hl7.org/fhir/StructureDefinition/Extension4.0.1, 5.0.0, 4.0.1
Type: Extension (a.k.a: http://hl7.org/fhir/StructureDefinition/Extension)
Type dependencies: 2
Elements