'Return a :class:`Path` instance of the unit rectangle
from (0, 0) to (1, 1).'

@classmethod
def unit_rectangle(cls):

    if (cls._unit_rectangle is None):
        cls._unit_rectangle = cls([[0.0, 0.0], [1.0, 0.0], [1.0, 1.0], [0.0, 1.0], [0.0, 0.0]], [cls.MOVETO, cls.LINETO, cls.LINETO, cls.LINETO, cls.CLOSEPOLY], readonly=True)
    return cls._unit_rectangle
