When extending Flex's built-in components, you might need to use 'mx_internal' namespace, to call the methods in the super class which are declared with 'mx_internal' namespace.
There are two ways to do this.
1. Import mx.core.mx_intertnal class and add 'use namespace mx_internal;' script just below your 'import' statements.
2. Otherwise, you can explicitly call the method by prefixing 'mx_internal::' before the method.
Happy coding!
