Returns the values for the requested sources of the requested chains.

Example request

{
  "parentIds": {
    "unique_chain_id": {
      "systems": [
        "system_5330c562-368b-4192-bbaf-db6638307783",
        "system_d2a0a05e-c0ec-4b39-a101-d3cb5f47bc03"
      ],
      "repos": [
        "repo_4ca781b6-154e-4bd0-8418-0c5debc07e54",
        "repo_fc4dfda7-2e97-433d-98ba-8af626a989b0"
      ]
    }
  }
}