code: def to_netcdf(self, filename, compress=True):
          
          mode = "w"  # overwrite first, then append
          if self._groups:  # check's whether a group is present or not.
              for group in self._groups:
                  data = getattr(self, group)
                  kwargs = {}
                  if compress:
                      kwargs["encoding"] = {var_name: {"zlib": True} for var_name in data.variables}
                  data.to_netcdf(filename, mode=mode, group=group, **kwargs)
                  data.close()
                  mode = "a"
          else:  # creates a netcdf file for an empty InferenceData object.
              empty_netcdf_file = nc.Dataset(filename, mode="w", format="NETCDF4")
              empty_netcdf_file.close()
          return filename
docs: Write InferenceData to file using netcdf4.
  
          Parameters
          ----------
          filename : str
              Location to write to
          compress : bool
              Whether to compress result. Note this saves disk space, but may make
              saving and loading somewhat slower (default: True).
  
          Returns
          -------
          str
              Location of netcdf file