Selects a slice of cells

        Parameters
        ----------
         * row_slc: Integer or Slice
        \tRows to be selected
         * col_slc: Integer or Slice
        \tColumns to be selected
         * add_to_selected: Bool, defaults to False
        \tOld selections are cleared if False

def select_slice(self, row_slc, col_slc, add_to_selected=False):
        """Selects a slice of cells

        Parameters
        ----------
         * row_slc: Integer or Slice
        \tRows to be selected
         * col_slc: Integer or Slice
        \tColumns to be selected
         * add_to_selected: Bool, defaults to False
        \tOld selections are cleared if False

        """

        if not add_to_selected:
            self.grid.ClearSelection()

        if row_slc == row_slc == slice(None, None, None):
            # The whole grid is selected
            self.grid.SelectAll()

        elif row_slc.stop is None and col_slc.stop is None:
            # A block is selected:
            self.grid.SelectBlock(row_slc.start, col_slc.start,
                                  row_slc.stop - 1, col_slc.stop - 1)
        else:
            for row in xrange(row_slc.start, row_slc.stop, row_slc.step):
                for col in xrange(col_slc.start, col_slc.stop, col_slc.step):
                    self.select_cell(row, col, add_to_selected=True)