code: def _cint(col, _map={base26(i): i - 1 for i in range(1, 257)}):
          
          try:
              return _map[col.upper()]
          except KeyError:
              raise ValueError(col)
docs: Return zero-based column index from bijective base26 string.
  
          >>> Coordinates._cint('Ab')
          27
  
          >>> Coordinates._cint('spam')
          Traceback (most recent call last):
              ...
          ValueError: spam