Constructor.
@param last_expected: in a perfect world, this is when the previous callback should have happened
@type last_expected: rospy.Time
@param last_real: when the callback actually happened
@type last_real: rospy.Time
@param current_expected: in a perfect world, this is when the current callback should have been called
@type current_expected: rospy.Time
@param last_duration: contains the duration of the last callback (end time minus start time) in seconds.
Note that this is always in wall-clock time.
@type last_duration: float
Definition at line 47 of file timer.py.