code: def save(self, overwrite=True):
          
          self.save_popset(overwrite=overwrite)
          self.save_signal()
docs: Saves PopulationSet and TransitSignal.
  
          Shouldn't need to use this if you're using
          :func:`FPPCalculation.from_ini`.
  
          Saves :class`PopulationSet` to ``[folder]/popset.h5]``
          and :class:`TransitSignal` to ``[folder]/trsig.pkl``.
  
          :param overwrite: (optional)
              Whether to overwrite existing files.