+ def __new__(cls, coordinates):
+ if isinstance(coordinates, Mapping):
+ coordinates = coordinates.items()
+ self = object().__new__(cls)
+ self._coordinates = OrderedDict()
+ for symbol, coordinate in sorted(coordinates,
+ key=lambda item: item[0].sortkey()):
+ if not isinstance(symbol, Symbol):
+ raise TypeError('symbols must be Symbol instances')
+ if not isinstance(coordinate, numbers.Real):
+ raise TypeError('coordinates must be real numbers')
+ self._coordinates[symbol] = coordinate
+ return self