code: def longest_bar_prefix_value(self):
          
          longest = 0
          for key, t in self.tasks.items():
              size = len(t.prefix)
              if size > longest:
                  longest = size
  
          return longest
docs: Calculates the longest progress bar prefix in order to keep all progress bars left-aligned.
          :return: Length of the longest task prefix in character unit.