code: def _sampleFromFaces(self):
      
      coordinates = [random.uniform(-1, 1) * dim / 2. for dim in self.dimensions]
      dim = random.choice(range(self.dimension))
      coordinates[dim] = self.dimensions[dim] / 2. * random.choice([-1, 1])
      return coordinates
docs: We start by sampling a dimension to "max out", then sample the sign and
      the other dimensions' values.