Firebase-找不到GetTokenResult、getExpirationTimestamp()

我正在尝试以下代码以获取Firebase用户的令牌及其过期时间:

fun refreshToken(apiBlock: (() -> Unit)? = null) {
    val firebaseUser = FirebaseAuth.getInstance().currentUser
    if (firebaseUser != null) {
        firebaseUser.getIdToken(false)
                .addOnCompleteListener { task ->
                    if (task.isSuccessful) {
                        generatedToken = task.result.token
                        val tokenExpirationTime = task.result.expirationTimestamp
                        apiBlock?.invoke()
                    } else {
                        // Handle error -> task.getException();
                    }
                }
    }
}

val tokenExpirationTime = task.result.expirationTimestamp

当我试图检查反编译类中是否存在此方法时,我无法获得任何此类方法:

package com.google.firebase.auth;

import android.support.annotation.Nullable;
import com.google.android.gms.common.internal.Hide;

public class GetTokenResult {
    private String zzeia;

    @Hide
    public GetTokenResult(String var1) {
        this.zzeia = var1;
    }

    @Nullable
    public String getToken() {
        return this.zzeia;
    }
}

但是根据 GetTokenResult class reference

getExpirationTimestamp()返回从epoch开始的时间(以毫秒为单位) 此ID令牌将过期的时间

我漏了什么吗?