code: def new(self, init=None):
          
          if self.count >= self.size:
              self.resize(self.count * 2)
          chunk = self.get(self.count)
          if init is not None:
              assert len(init) == self.chunk_size
              chunk[0:self.chunk_size] = init
          self.count += 1
          return chunk
docs: Return the last currently unused chunk, resizing if needed.
  
          If init is passed, chunk will be initialised to that data