code: def _make_map(self, limit):
          
          ny = 2000
          y = numpy.random.uniform(0., 1., (ny,1))
          limit = numpy.arctan(limit)
          m = AdaptiveMap([[-limit, limit]], ninc=100)
          theta = numpy.empty(y.shape, float)
          jac = numpy.empty(y.shape[0], float)
          for itn in range(10):
              m.map(y, theta, jac)
              tan_theta = numpy.tan(theta[:, 0])
              x = self.scale * tan_theta
              fx = (tan_theta ** 2 + 1) * numpy.exp(-(x ** 2) / 2.)
              m.add_training_data(y, (jac * fx) ** 2)
              m.adapt(alpha=1.5)
          return numpy.array(m.grid[0])
docs: Make vegas grid that is adapted to the pdf.