docs: def _dqdv_split_frames(cell, tidy=False, **kwargs):
      """Returns dqdv data as pandas.DataFrames for all cycles.
  
          Args:
              cell (CellpyData-object).
              tidy (bool): return in wide format if False (default),
                  long (tidy) format if True.
  
          Returns:
              (charge_ica_frame, discharge_ica_frame) where the frames are
              pandas.DataFrames where the first column is voltage ('v') and
              the following columns are the incremental capcaity for each
              cycle (multi-indexed, where cycle number is on the top level).
  
          Example:
              >>> from cellpy.utils import ica
              >>> charge_ica_df, dcharge_ica_df = ica.ica_frames(my_cell)
              >>> charge_ica_df.plot(x=("voltage", "v"))
  
      """
      charge_dfs, cycles, minimum_v, maximum_v = _collect_capacity_curves(
          cell,
          direction="charge"
      )
      # charge_df = pd.concat(
      # charge_dfs, axis=1, keys=[k.name for k in charge_dfs])
  
      ica_charge_dfs = _make_ica_charge_curves(
          charge_dfs, cycles, minimum_v, maximum_v,
          **kwargs,
      )
      ica_charge_df = pd.concat(
          ica_charge_dfs,
          axis=1,
          keys=[k.name for k in ica_charge_dfs]
      )
  
      dcharge_dfs, cycles, minimum_v, maximum_v = _collect_capacity_curves(
          cell,
          direction="discharge"
      )
      ica_dcharge_dfs = _make_ica_charge_curves(
          dcharge_dfs, cycles, minimum_v, maximum_v,
          **kwargs,
      )
      ica_discharge_df = pd.concat(
          ica_dcharge_dfs,
          axis=1,
          keys=[k.name for k in ica_dcharge_dfs]
      )
      ica_charge_df.columns.names = ["cycle", "value"]
      ica_discharge_df.columns.names = ["cycle", "value"]
  
      if tidy:
          ica_charge_df = ica_charge_df.melt(
              "voltage",
              var_name="cycle",
              value_name="dq",
              col_level=0
          )
          ica_discharge_df = ica_discharge_df.melt(
              "voltage",
              var_name="cycle",
              value_name="dq",
              col_level=0
          )
  
      return ica_charge_df, ica_discharge_df