After installing google maps plugin "object(....) is not a function"

hi
I was trying to add google maps to an app that I was working on and after running these commands :

ionic cordova plugin add cordova-plugin-googlemaps \
  --variable API_KEY_FOR_ANDROID="key" \
  --variable API_KEY_FOR_IOS="key"

npm install @ionic-native/core @ionic-native/google-maps

I get this error:

 Runtime error
    Object(...) is not a function

even though I didn’t use the plugin in my code yet !

here is my package.json :

{
  "name": "cake-driver",
  "version": "0.0.1",
  "author": "Ionic Framework",
  "homepage": "http://ionicframework.com/",
  "private": true,
  "scripts": {
    "start": "ionic-app-scripts serve",
    "clean": "ionic-app-scripts clean",
    "build": "ionic-app-scripts build",
    "lint": "ionic-app-scripts lint"
  },
  "dependencies": {
    "@angular/animations": "5.2.11",
    "@angular/common": "5.2.11",
    "@angular/compiler": "5.2.11",
    "@angular/compiler-cli": "5.2.11",
    "@angular/core": "5.2.11",
    "@angular/forms": "5.2.11",
    "@angular/http": "5.2.11",
    "@angular/platform-browser": "5.2.11",
    "@angular/platform-browser-dynamic": "5.2.11",
    "@ionic-native/base64": "^4.20.0",
    "@ionic-native/core": "^5.0.0",
    "@ionic-native/google-maps": "^4.20.0",
    "@ionic-native/image-picker": "^4.20.0",
    "@ionic-native/onesignal": "^4.20.0",
    "@ionic-native/splash-screen": "~4.18.0",
    "@ionic-native/status-bar": "~4.18.0",
    "@ionic/pro": "2.0.4",
    "@ionic/storage": "^2.2.0",
    "com-badrit-base64": "0.2.0",
    "cordova-android": "7.1.4",
    "cordova-ios": "4.5.5",
    "cordova-plugin-device": "^2.0.2",
    "cordova-plugin-googlemaps": "2.5.0",
    "cordova-plugin-ionic-keyboard": "^2.1.3",
    "cordova-plugin-ionic-webview": "^2.3.3",
    "cordova-plugin-splashscreen": "^5.0.2",
    "cordova-plugin-statusbar": "^2.4.2",
    "cordova-plugin-telerik-imagepicker": "2.2.2",
    "cordova-plugin-whitelist": "^1.3.3",
    "cordova-sqlite-storage": "3.0.0",
    "ionic-angular": "3.9.2",
    "ionicons": "3.0.0",
    "onesignal-cordova-plugin": "2.4.6",
    "rxjs": "6.0.0",
    "rxjs-compat": "^6.4.0",
    "sw-toolbox": "3.6.0",
    "zone.js": "0.8.26"
  },
  "devDependencies": {
    "@ionic/app-scripts": "3.2.1",
    "typescript": "~2.6.2"
  },
  "description": "An Ionic project",
  "cordova": {
    "plugins": {
      "onesignal-cordova-plugin": {},
      "cordova-plugin-whitelist": {},
      "cordova-plugin-statusbar": {},
      "cordova-plugin-device": {},
      "cordova-plugin-splashscreen": {},
      "cordova-plugin-ionic-webview": {
        "ANDROID_SUPPORT_ANNOTATIONS_VERSION": "27.+"
      },
      "cordova-plugin-ionic-keyboard": {},
      "cordova-plugin-telerik-imagepicker": {
        "PHOTO_LIBRARY_USAGE_DESCRIPTION": "yoWe need this permission to get the needed photos"
      },
      "com-badrit-base64": {},
      "cordova-sqlite-storage": {},
      "cordova-plugin-googlemaps": {
        "API_KEY_FOR_ANDROID": "AIzaSyCOd-Z643z1lP19CDHw-tr3eBugmpAXz8k",
        "API_KEY_FOR_IOS": "AIzaSyDFr-FqOKG_WDNKYggLeCJw8yPPkHOyR5Q"
      }
    },
    "platforms": [
      "android"
    ]
  }
}