public <T> List<T> getConfiguredInstances(String key, Class<T> t) {
        return getConfiguredInstances(key, t, Collections.emptyMap());
    }
Get a list of configured instances of the given class specified by the given configuration key. The configuration
may specify either null or an empty string to indicate no configured instances. In both cases, this method
returns an empty list to indicate no configured instances.

@param key The configuration key for the class
@param t   The interface the class should implement
@return The list of configured instances
clients/src/main/java/org/apache/kafka/common/config/AbstractConfig.java