code: public boolean isValid() {
          getTemplateClass();
          if (findExecuteMethod() == null)
              throw new IllegalArgumentException("Cannot locate compiled template entry point.");
           Class<?>[] p = mExecuteMethod.getParameterTypes();
           mSubParam = false;
           mRuntimeContext = p[0];
           return mRuntimeContext.isInterface();
      }
docs: Checks if the compiled template class is a precomiled
  template (i.e. it's runtime context is an interface, not a generated MergedContext)
  
  @return true if the template class is found, has the proper template execute method,
  and the first parameter to the execute method (the runtime context for the template) is an interface