...
+--rw oam
|  +--rw bfd {vpn-common:bfd}?
|     +--rw session-type?               identityref
|     +--rw desired-min-tx-interval?    uint32
|     +--rw required-min-rx-interval?   uint32
|     +--rw local-multiplier?           uint8
|     +--rw holdtime?                   uint32
|     +--rw profile?                    leafref
|     +--rw authentication!
|     |  +--rw key-chain?    key-chain:key-chain-ref
|     |  +--rw meticulous?   boolean
|     +--rw status
|        +--rw admin-status
|           |  +--rw status?         identityref
|           |  +--rw last-change?   yang:date-and-time
|           +--ro oper-status
|              +--ro status?         identityref
|              +--ro last-change?   yang:date-and-time
...