def digest(type = :sha1)
      case type
      when :sha1
        Digest::SHA1.hexdigest(@bindata)
      when :sha256
        Digest::SHA256.hexdigest(@bindata)
      when :md5
        Digest::MD5.hexdigest(@bindata)
      else
        raise ArgumentError
      end
    end
def digest(type = :sha1)
      case type
      when :sha1
        Digest::SHA1.hexdigest(@bindata)
      when :sha256
        Digest::SHA256.hexdigest(@bindata)
      when :md5
        Digest::MD5.hexdigest(@bindata)
      else
        raise ArgumentError
      end
    end
return hex digest string of apk file
 @param [Symbol] type hash digest type(:sha1, sha256, :md5)
 @return [String] hex digest string
 @raise [ArgumentError] type is knknown type