class_docstr: The problem of fitting the sum of exponentials with linear degrees
  to data, [1]_.
  
  Number of variables --- 5, number of residuals --- 33, no bounds.
  
  .. [1] Brett M. Averick et al. "The MINPACK-2 Test Problem Collection",
         p. 26
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code: def fun(self, x):
      return (
          x[0]
          + x[1] * np.exp(-x[3] * self.t)
          + x[2] * np.exp(-x[4] * self.t)
          - self.y
      )
  
imports: import inspect
  import sys
  import numpy
  from numpy.polynomial.chebyshev import Chebyshev
  from scipy.integrate import odeint
label_desc: Use image node_id 2 for calling the ExponentialFitting obj's underlying member method code with example usage: obj.fun(x) and returns: unknown