static List<Map.Entry<String, Method>> fieldGetters(final Class<?> iface) {
        final ArrayList<Map.Entry<String, Method>> builder = new ArrayList<>();
        for (Method method : iface.getMethods()) {
            String methodName = method.getName();
            String fieldName = getterFieldNameOrNull(methodName);
            if (fieldName != null && hasExpectedArgumentLength(method, 0)
                    && (!method.isDefault() || method.getAnnotation(Config.class) != null)) {
                // If the method has default implementation, and @Config is not annotated there, the method is kept.
                builder.add(new AbstractMap.SimpleImmutableEntry<>(fieldName, method));
            }
        }
        return Collections.unmodifiableList(builder);
    }
Returns a Multimap from fieldName Strings to their getter Methods.

It expects to be called only from TaskSerDe. Multimap is used inside org.embulk.config.
embulk-deps/src/main/java/org/embulk/deps/config/TaskInvocationHandler.java