code: def clear_bg(self, which_data=("amplitude", "phase"), keys="fit"):
          
          which_data = QPImage._conv_which_data(which_data)
          if isinstance(keys, str):
              # make sure keys is a list of strings
              keys = [keys]
  
          # Get image data for clearing
          imdats = []
          if "amplitude" in which_data:
              imdats.append(self._amp)
          if "phase" in which_data:
              imdats.append(self._pha)
          if not imdats:
              msg = "`which_data` must contain 'phase' or 'amplitude'!"
              raise ValueError(msg)
          # Perform clearing of backgrounds
          for imdat in imdats:
              for key in keys:
                  imdat.del_bg(key)
docs: Clear background correction
  
          Parameters
          ----------
          which_data: str or list of str
              From which type of data to remove the background
              information. The list contains either "amplitude",
              "phase", or both.
          keys: str or list of str
              Which type of background data to remove. One of:
  
              - "fit": the background data computed with
                :func:`qpimage.QPImage.compute_bg`
              - "data": the experimentally obtained background image