code: func NestedInt64(obj map[string]interface{}, fields ...string) (int64, bool, error) {
  	val, found, err := NestedFieldNoCopy(obj, fields...)
  	if !found || err != nil {
  		return 0, found, err
  	}
  	i, ok := val.(int64)
  	if !ok {
  		return 0, false, fmt.Errorf("%v accessor error: %v is of the type %T, expected int64", jsonPath(fields), val, val)
  	}
  	return i, true, nil
  }
docs: // NestedInt64 returns the int64 value of a nested field.
  // Returns false if value is not found and an error if not an int64.