code: def deriv(self, t, theta):
      t = np.asarray(t)
      tmp = np.exp(-t * theta)
      return -theta * tmp / (tmp - 1)
  
imports: import warnings
  import numpy
  from scipy.special import expm1, gamma
label_desc: Use image node_id 3 for calling the TransfFrank obj's underlying member method code with example usage: obj.deriv(t, theta) and returns: unknown