code: def require_data(self, product_type):
      
      self._dependencies.add(product_type)
      self._context.products.require_data(product_type)
docs: Schedules the tasks that produce product_type to be executed before the requesting task.
  
      There must be at least one task that produces the required product type, or the
      dependencies will not be satisfied.
  
      :API: public