@Nullable
    public static Scheme tryParse(@Nullable String scheme) {
        if (scheme == null) {
            return null;
        }
        final String lowercaseScheme = Ascii.toLowerCase(scheme);
        final Scheme parsedScheme = SCHEMES.get(lowercaseScheme);
        if (parsedScheme != null) {
            return parsedScheme;
        }
        return SCHEMES.get(SerializationFormat.NONE.uriText() + '+' + lowercaseScheme);
    }
Parses the specified {@link String} into a {@link Scheme}. This method will return the same
{@link Scheme} instance for equal values of {@code scheme}.

@return {@code null} if the specified {@link String} could not be parsed or
        there is no such {@link Scheme} available
core/src/main/java/com/linecorp/armeria/common/Scheme.java