def start_at=(start_at)
      if start_at.nil?
        fail ArgumentError, "start_at cannot be nil"
      end

      if start_at.to_s.length < 1
        fail ArgumentError, "invalid value for 'start_at', the character length must be great than or equal to 1."
      end

      @start_at = start_at
    end
def start_at=(start_at)
      if start_at.nil?
        fail ArgumentError, "start_at cannot be nil"
      end

      if start_at.to_s.length < 1
        fail ArgumentError, "invalid value for 'start_at', the character length must be great than or equal to 1."
      end

      @start_at = start_at
    end
Custom attribute writer method with validation
 @param [Object] start_at Value to be assigned