def check(activity)
      unless @first_lap_index
        Log.fatal 'first_lap_index is not set'
      end
      unless @num_laps
        Log.fatal 'num_laps is not set'
      end
      @first_lap_index.upto(@first_lap_index - @num_laps) do |i|
        if (lap = activity.lap[i])
          @laps << lap
        else
          Log.fatal "Session references lap #{i} which is not contained in "
                    "the FIT file."
        end
      end
    end
def check(activity)
      unless @first_lap_index
        Log.fatal 'first_lap_index is not set'
      end
      unless @num_laps
        Log.fatal 'num_laps is not set'
      end
      @first_lap_index.upto(@first_lap_index - @num_laps) do |i|
        if (lap = activity.lap[i])
          @laps << lap
        else
          Log.fatal "Session references lap #{i} which is not contained in "
                    "the FIT file."
        end
      end
    end
Create a new Session object.
 @param laps [Array of Laps] Laps to associate with the Session.
 @param first_lap_index [Fixnum] Index of the first Lap in this Session.
 @param field_values [Hash] Hash that provides initial values for certain
        fields.
 Perform some basic consistency and logical checks on the object. Errors
 are reported via the Log object.