const relationships = [
  {
     externalId: 'some_relationship',
     sourceExternalId: 'some_source_external_id',
     sourceType: 'asset' as const,
     targetExternalId: 'some_target_external_id',
     targetType: 'event' as const
  }
];
const createdRelationships = await client.relationships.create(relationships);

{
  "items": [
    {
      "externalId": "<string>",
      "sourceExternalId": "<string>",
      "sourceType": "asset",
      "targetExternalId": "<string>",
      "targetType": "asset",
      "createdTime": 1730204346000,
      "lastUpdatedTime": 1730204346000,
      "startTime": 1730204346000,
      "endTime": 1730204346000,
      "confidence": 0.5,
      "dataSetId": 4503599627370496,
      "labels": [
        {
          "externalId": "my.known.id"
        }
      ]
    }
  ]
}