docs: def set_cellpy_datadir(self, directory=None):
          """Set the directory containing .hdf5-files.
  
          Used for setting directory for looking for hdf5-files.
          A valid directory name is required.
  
          Args:
              directory (str): path to hdf5-directory
  
          Example:
              >>> d = CellpyData()
              >>> directory = "MyData/HDF5"
              >>> d.set_raw_datadir(directory)
  
          """
  
          if directory is None:
              self.logger.info("no directory name given")
              return
          if not os.path.isdir(directory):
              self.logger.info("directory does not exist")
              return
          self.cellpy_datadir = directory