decoding a json with variable keys

[pdegouville]

I am trying to decode a JSON like this one with Himotoki in Swift 3

next: [
          {
            question: 'Fréquence',
            condition: { '==': ['answer', 'Actions'] },
          },
          {
            question: 'Fréquence',
            condition: { '>=': ['answer', 'Stop'] },
          },
          {
            question: 'Risque',
            condition: { '<=': ['answer', 'nul'] }
          }
        ]

In the condition, there is an object that looks like a dictionary, since the field name changes ('==', '<=', '>=, ...). The value is then an array of string

I have tried to decode like this

typealias ConditionType = [String]

extension ConditionType: Decodable {}

struct NextItem {
    let question: String?
    let condition: [String : ConditionType]?
}

extension NextItem: Decodable {
    static func decode(_ e: Extractor) throws -> NextItem {

        return try NextItem(
            question:  e <|? "question",
            condition: e <|-|? "condition"
        )
    }
}

I do not not how to decode the ConditionType since there is no field name for the array