public static AsciiString of(CharSequence name) {
        if (name instanceof AsciiString) {
            return of((AsciiString) name);
        }

        final String lowerCased = Ascii.toLowerCase(requireNonNull(name, "name"));
        final AsciiString cached = map.get(lowerCased);
        if (cached != null) {
            return cached;
        }

        return validate(AsciiString.cached(lowerCased));
    }
Lower-cases and converts the specified header name into an {@link AsciiString}. If {@code "name"} is
a known header name, this method will return a pre-instantiated {@link AsciiString} to reduce
the allocation rate of {@link AsciiString}.

@throws IllegalArgumentException if the specified {@code name} is not a valid header name.
core/src/main/java/com/linecorp/armeria/common/HttpHeaderNames.java