你可以创建一个新的结构（在本例中，我们将调用result），并将其传递给Gson serialize：

fun main() {
    val structure: Set<List<Map<String, Any>>> = setOf(
        listOf(
            mapOf("id" to "obj1Id", "property2" to listOf(setOf("element1"), setOf("element2"))),
            mapOf("id" to "obj2Id", "property2" to listOf(setOf("element1"), setOf("element2"))),
            mapOf("propertyName3" to "propertyValue3"),
            mapOf("propertyName4" to "propertyValue4"),
        )
    )
    println(structure)
    // Outputs [[{id=obj1Id, property2=[[element1], [element2]]}, {id=obj2Id, property2=[[element1], [element2]]}, {propertyName3=propertyValue3}, {propertyName4=propertyValue4}]]

    // Creates a hash map where we'll add the entries of the original structure
    val result: MutableMap<String, Any> = mutableMapOf()

    // Iterating over each list inside the first-nested level
    structure.forEach { list ->
        // Iterating over each map inside the second-nested level 
        list.forEach { map ->
            // Check if this map has an `id` key 
            // If it has, evaluate to its value, else to null
            val idValue = map["id"] as String?

            // If there is an `id` key
            if (idValue != null) {
                // Add its value to its respective property
                result[idKey] = map.filterKeys { key -> key != "id" }
                // Or, if you need to add only the "property2" key:
                // result[idKey] = mapOf("property2" to map["property2"])

            } else {
                // Add all these entries to the result map
                result.putAll(map)
                // Or, if you need to add only the keys starting with "propertyName":
                // map.filterKeys { key -> key.startsWith("propertyName") }.forEach(result::put)
            }
        }
    }
    println(result)
    // Outputs {obj1Id={property2=[[element1], [element2]]}, obj2Id={property2=[[element1], [element2]]}, propertyName3=propertyValue3, propertyName4=propertyValue4}
}