docs: def dqdv_frames(cell, split=False, **kwargs):
      """Returns dqdv data as pandas.DataFrame(s) for all cycles.
  
              Args:
                  cell (CellpyData-object).
                  split (bool): return one frame for charge and one for
                      discharge if True (defaults to False).
  
              Returns:
                  pandas.DataFrame(s) with the following columns:
                      cycle: cycle number (if split is set to True).
                      voltage: voltage
                      dq: the incremental capacity
  
              Example:
                  >>> from cellpy.utils import ica
                  >>> charge_df, dcharge_df = ica.ica_frames(my_cell, split=True)
                  >>> charge_df.plot(x=("voltage", "v"))
      """
      # TODO: should add option for normalising based on first cycle capacity
      # this is e.g. done by first finding the first cycle capacity (nom_cap)
      # (or use nominal capacity given as input) and then propagating this to
      # Converter using the key-word arguments
      #   normalize=True, normalization_factor=1.0, normalization_roof=nom_cap
  
      if split:
          return _dqdv_split_frames(cell, tidy=True, **kwargs)
      else:
          return _dqdv_combinded_frame(cell, **kwargs)