One of the most tricky ASN.1 excerpt :

E-RABDataForwardingItemIEs S1AP-PROTOCOL-IES ::= {
    { ID id-E-RABDataForwardingItem   CRITICALITY ignore   TYPE E-RABDataForwardingItem PRESENCE mandatory },
    ...
}

E-RABSubjecttoDataForwardingList ::= E-RAB-IE-ContainerList { {E-RABDataForwardingItemIEs} }

E-RAB-IE-ContainerList { S1AP-PROTOCOL-IES : IEsSetParam } ::=
    ProtocolIE-ContainerList { 1, maxnoofE-RABs, {IEsSetParam} }

ProtocolIE-ContainerList {INTEGER : lowerBound, INTEGER : upperBound, S1AP-PROTOCOL-IES : IEsSetParam} ::=
    SEQUENCE (SIZE (lowerBound..upperBound)) OF
    ProtocolIE-SingleContainer {{IEsSetParam}}

ProtocolIE-SingleContainer {S1AP-PROTOCOL-IES : IEsSetParam} ::=
    ProtocolIE-Field {{IEsSetParam}}

ProtocolIE-Field {S1AP-PROTOCOL-IES : IEsSetParam} ::= SEQUENCE {
    id          S1AP-PROTOCOL-IES.&id           ({IEsSetParam}),
    criticality S1AP-PROTOCOL-IES.&criticality  ({IEsSetParam}{@id}),
    value       S1AP-PROTOCOL-IES.&Value        ({IEsSetParam}{@id})
}