code: def set_cols_valign(self, array):
          
  
          self._check_row_size(array)
          self._valign = array
          return self
docs: Set the desired columns vertical alignment
  
          - the elements of the array should be either "t", "m" or "b":
  
              * "t": column aligned on the top of the cell
              * "m": column aligned on the middle of the cell
              * "b": column aligned on the bottom of the cell