code: func (c *CacheLazyFill) fetchEntityFromAPI(entityType, guid string) (*entity, error) {
  	var md struct {
  		Entity *entity `json:"entity"`
  	}
  	err := c.makeRequestAndDecodeJSON(fmt.Sprintf("/v2/%s/%s", entityType, guid), &md)
  	if err != nil {
  		return nil, err
  	}
  	return md.Entity, nil
  }
docs: // both entityType and guid must have been validated by the caller