docs: def data(self, index, role=Qt.DisplayRole):
          """Cell content"""
          if not index.isValid():
              return None
          if role == Qt.DisplayRole or role == Qt.EditRole:
              return ' '
          if role == Qt.BackgroundColorRole:
              color = self.color_da[index.row(), index.column()].values
              return QtGui.QColor.fromRgbF(*color)
          return None