code: def build_duration_pretty(self):
          
          from ambry.util import pretty_time
          from time import time
  
          if not self.state.building:
              return None
  
          built = self.state.built or time()
  
          try:
              return pretty_time(int(built) - int(self.state.building))
          except TypeError:  # one of the values is  None or not a number
              return None
docs: Return the difference between build and build_done states, in a human readable format