new_contents: from scipy import imag, real, log, sqrt, random
  from scipy.interpolate import RectBivariateSpline
  
  
  class nelson:
      def __init__(self, x, t, psi, xinit):
          imz, rez = imag(log(psi)), real(log(psi))
          self.realSpline, self.imagSpline = RectBivariateSpline(t, x, rez), RectBivariateSpline(t, x, imz)
          self.t = 0
          self.x = xinit
          self.n = len(xinit)
  
      def drift(self, x, t):
          re = self.realSpline.ev(t, x, dx=1)
          im = self.imagSpline.ev(t, x, dx=1)
          return (re + im)/2
  
      def run(self, dt):
          rand = sqrt(0.5) * random.normal(scale=dt, size=self.n)
          self.x += self.drift(self.x, self.t) * dt + rand
          return self.x
  
subject: add nelson