Extrinsic 979-1

{
  "heartbeat": {
    "blockNumber": 978,
    "sessionIndex": 16,
    "validatorsLen": 4,
    "authorityIndex": 2
  },
  "signature": "0x3091fa67a16be6e4bfcde760cb22b1de59d0ba0839ed927950705266dcc6c52b91ed6a98fe7c5b0d9ddf1d18bb2bba1b340033700f674f25bfc2190c6f2ec58b"
}