default Scheme validateScheme(Scheme scheme) {
        requireNonNull(scheme, "scheme");

        final Set<Scheme> supportedSchemes = supportedSchemes();
        if (!supportedSchemes.contains(scheme)) {
            throw new IllegalArgumentException(
                    "Unsupported scheme: " + scheme + " (expected: " + supportedSchemes + ')');
        }

        return scheme;
    }
Makes sure the specified {@link Scheme} is supported by this {@link ClientFactory}.

@param scheme the {@link Scheme} of the server endpoint
@return the specified {@link Scheme}

@throws IllegalArgumentException if the {@link Scheme} is not supported by this {@link ClientFactory}
core/src/main/java/com/linecorp/armeria/client/ClientFactory.java