code: def copy_traj_attributes(target, origin, start):
      
  
      # The list of copied attributes can be extended here with time
      # Or perhaps ask the mdtraj guys to implement something similar?
      stop = start+origin.n_frames
  
      target.xyz[start:stop] = origin.xyz
      target.unitcell_lengths[start:stop] = origin.unitcell_lengths
      target.unitcell_angles[start:stop] = origin.unitcell_angles
      target.time[start:stop] = origin.time
  
      return target
docs: Inserts certain attributes of origin into target
      :param target: target trajectory object
      :param origin: origin trajectory object
      :param start: :py:obj:`origin` attributes will be inserted in :py:obj:`target` starting at this index
      :return: target: the md trajectory with the attributes of :py:obj:`origin` inserted