Returns a list of lists containing all cells' values as strings.

        .. note::

            Empty trailing rows and columns will not be included.

def get_all_values(self):
        """Returns a list of lists containing all cells' values as strings.

        .. note::

            Empty trailing rows and columns will not be included.
        """

        data = self.spreadsheet.values_get(self.title)

        try:
            return fill_gaps(data['values'])
        except KeyError:
            return []