code: func (c *Client) AddReading(r contract.Reading) (id string, err error) {
  	conn := c.Pool.Get()
  	defer conn.Close()
  
  	if r.Id != "" {
  		_, err = uuid.Parse(r.Id)
  		if err != nil {
  			return "", db.ErrInvalidObjectId
  		}
  	}
  	return addReading(conn, true, r)
  }
docs: // Post a new reading
  // Check if valuedescriptor exists in the database