code: @Beta
    public static GoogleCredential fromStream(InputStream credentialStream) throws IOException {
       return fromStream(
          credentialStream,
          Utils.getDefaultTransport(),
          Utils.getDefaultJsonFactory());
    }
docs: {@link Beta} <br/>
  Return a credential defined by a Json file.
  
  @param credentialStream the stream with the credential definition.
  @return the credential defined by the credentialStream.
  @throws IOException if the credential cannot be created from the stream.