public static Http2Headers toNettyHttp2ClientHeaders(HttpHeaders inputHeaders) {
        final int headerSizeHint = inputHeaders.size() + 3; // User_Agent, :scheme and :authority.
        final Http2Headers outputHeaders = new DefaultHttp2Headers(false, headerSizeHint);
        toNettyHttp2Client(inputHeaders, outputHeaders, false);
        return outputHeaders;
    }
Converts the specified Armeria HTTP/2 request headers into Netty HTTP/2 headers.

@param inputHeaders the HTTP/2 request headers to convert.
core/src/main/java/com/linecorp/armeria/internal/common/ArmeriaHttpUtil.java