private static void addExtensionToMap(String fqExtensionName, Class extensionClass,
                                          Map<String, Class> siddhiExtensionsMap) {
        Class previousClass = null;
        Class existingValue = siddhiExtensionsMap.get(fqExtensionName);
        if (existingValue == null) {
            previousClass = siddhiExtensionsMap.put(fqExtensionName, extensionClass);
        }
        if (previousClass != null) {
            log.warn("Dropping extension '" + extensionClass + "' as '" + previousClass + "' was already " +
                    "loaded with the same namespace and name '" + fqExtensionName + "'");
        }
    }
Adding extensions to Siddhi siddhiExtensionsMap.

@param fqExtensionName     fully qualified extension name (namespace:extensionName or extensionName)
@param extensionClass      extension class
@param siddhiExtensionsMap reference map for the Siddhi extension
modules/siddhi-core/src/main/java/io/siddhi/core/util/SiddhiExtensionLoader.java