code: def isfld(xmethod, dmethod, opt):
      
  
      fld = ['Iter', 'ObjFun', 'DFid', 'RegL1', 'Cnstr']
      if xmethod == 'admm':
          fld.extend(['XPrRsdl', 'XDlRsdl', 'XRho'])
      else:
          if opt['CBPDN', 'BackTrack', 'Enabled']:
              fld.extend(['X_F_Btrack', 'X_Q_Btrack', 'X_ItBt', 'X_L',
                          'X_Rsdl'])
          else:
              fld.extend(['X_L', 'X_Rsdl'])
      if dmethod != 'fista':
          fld.extend(['DPrRsdl', 'DDlRsdl', 'DRho'])
      else:
          if opt['CCMOD', 'BackTrack', 'Enabled']:
              fld.extend(['D_F_Btrack', 'D_Q_Btrack', 'D_ItBt', 'D_L',
                          'D_Rsdl'])
          else:
              fld.extend(['D_L', 'D_Rsdl'])
      fld.append('Time')
      return fld
docs: Return ``isfld`` argument for ``.IterStatsConfig`` initialiser.