{
  "transformation_type": "combine_linear",
  "output_feature_name": "number_of_ltcs",
  "subfeature": {
    "asthma": {
      "weight": 1,
      "source_table": "ltc",
      "transformation_type": "present",
      "grouping_column": "id",
      "filter": {
        "column": "asthma",
        "type": "date_gt",
        "value": "1800-01-01"
      }
    },
    "diabetes": {
      "weight": 1,
      "source_table": "ltc",
      "transformation_type": "present",
      "grouping_column": "id",
      "filter": {
        "column": "diabetes",
        "type": "date_gt",
        "value": "1800-01-01"
      }
    },
    "parkinsons": {
      "weight": 1,
      "source_table": "ltc",
      "transformation_type": "present",
      "grouping_column": "id",
      "filter": {
        "column": "parkinsons",
        "type": "date_gt",
        "value": "1800-01-01"
      }
    }
  }
}
