docs: def get_start_time(self):
          """
          Return the start time of the entry as a :class:`datetime.time` object.
          If the start time is `None`, the end time of the previous entry will be
          returned instead. If the current entry doesn't have a duration in the
          form of a tuple, if there's no previous entry or if the previous entry
          has no end time, the value `None` will be returned.
          """
          if not isinstance(self.duration, tuple):
              return None
  
          if self.duration[0] is not None:
              return self.duration[0]
          else:
              if (self.previous_entry and
                      isinstance(self.previous_entry.duration, tuple) and
                      self.previous_entry.duration[1] is not None):
                  return self.previous_entry.duration[1]
  
          return None