code: def _sampleFromVertices(self):
      
      coordinates = [
        self.dimensions[0] / 2. * random.choice([-1, 1]),
        self.dimensions[1] / 2. * random.choice([-1, 1]),
        self.dimensions[2] / 2. * random.choice([-1, 1]),
      ]
      return coordinates
docs: We start by sampling dimensions to "max out", then sample the sign and
      the other dimensions' values.