def metadata=(metadata)
      @metadata = metadata.map { |k, str| [k, str.to_s] }.to_h
    end
def metadata=(metadata)
      @metadata = metadata.map { |k, str| [k, str.to_s] }.to_h
    end
Ensure all metadata values are strings as HTTP/2 requires string values for transport

 @param [Hash] metadata The existing metadata hash
 @return [Hash] The newly set metadata