code: def Nelson(b, x, y=None):
      b = read_params(b)
      x1 = x[:, 0]
      x2 = x[:, 1]
      model = b[0] - b[1] * x1 * exp(-b[2] * x2)
      return model - log(y)
  
imports: import os
  from numpy import arctan, array, cos, exp, log, sin
  from lmfit import Parameters
label_desc: Use image node_id 19 for calling a global function with example usage: Nelson(b, x, y) and returns: unknown