我无法解决此问题。请指导我。我收到以下错误：
CommandInvokationFailure: Unable to convert classes into dex format.
/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/bin/java -Xmx2048M -Dcom.android.sdkmanager.toolsdir="/Volumes/HDD/Softwares/Android-sdk-macosx/tools" -Dfile.encoding=UTF8 -jar "/Applications/Unity_unknown/PlaybackEngines/AndroidPlayer/Tools/sdktools.jar" -
stderr[Uncaught translation error: java.lang.IllegalArgumentException: already added: Lcom/google/android/gms/common/util/VisibleForTesting;
1 error; aborting]
可能是什么原因造成的？