curl --request POST \
  --url https://example.com/mempool \
  --header 'Content-Type: application/json' \
  --data '{
  "network_identifier": {
    "blockchain": "bitcoin",
    "network": "mainnet",
    "sub_network_identifier": {
      "network": "shard 1",
      "metadata": {
        "producer": "0x52bc44d5378309ee2abf1539bf71de1b7d7be3b5"
      }
    }
  },
  "metadata": {}
}'

{
  "transaction_identifiers": [
    {
      "hash": "0x2f23fd8cca835af21f3ac375bac601f97ead75f2e79143bdf71fe2c4be043e8f"
    }
  ]
}