docs: def _unpackXY(x, y):
      """If x is a sequence and y is None, returns x[0], y[0]. Else, returns x, y.
  
      On functions that receive a pair of x,y coordinates, they can be passed as
      separate arguments, or as a single two-element sequence.
      """
      if isinstance(x, str):
          # x parameter is the string of an image filename to find and click on:
          x, y = center(locateOnScreen(x))
  
      elif isinstance(x, collectionsSequence):
          if len(x) == 2:
              if y is None:
                  x, y = x
              else:
                  raise ValueError('When passing a sequence at the x argument, the y argument must not be passed (received {0}).'.format(repr(y)))
          else:
              raise ValueError('The supplied sequence must have exactly 2 elements ({0} were received).'.format(len(x)))
      else:
          pass # x and y are just number values
  
      return x, y