code: public ProcessorDef getExtends() throws BuildException {
      if (this.extendsRef != null) {
        final Object obj = this.extendsRef.getReferencedObject(getProject());
        if (!getClass().isInstance(obj)) {
          throw new BuildException("Referenced object " + this.extendsRef.getRefId() + " not correct type, is "
              + obj.getClass().getName() + " should be " + getClass().getName());
        }
        return (ProcessorDef) obj;
      }
      return null;
    }
docs: Gets the ProcessorDef specified by the extends attribute
  
  @return Base ProcessorDef, null if extends is not specified
  @throws BuildException
  if reference is not same type object