docs: def parse_table_column_properties(doc, cell, prop):
      "Parse table column properties."
  
      if not cell:
          return
  
      grid = prop.find(_name('{{{w}}}gridSpan'))
  
      if grid is not None:
          cell.grid_span = int(grid.attrib[_name('{{{w}}}val')])
  
      vmerge = prop.find(_name('{{{w}}}vMerge'))
  
      if vmerge is not None:
          if _name('{{{w}}}val') in vmerge.attrib:
              cell.vmerge = vmerge.attrib[_name('{{{w}}}val')]
          else:
              cell.vmerge = ""