protected SubjectContext getSubjectContext() {
            return this.subjectContext;
        }
Returns the backing context used to build the {@code Subject} instance, available to subclasses
since the {@code context} class attribute is marked as {@code private}.

@return the backing context used to build the {@code Subject} instance, available to subclasses.
core/src/main/java/org/apache/shiro/subject/Subject.java