class_docstr: The problem of fitting kinetic parameters for an enzyme reaction, [1]_.
  
  Number of variables --- 4, number of residuals --- 11, no bounds.
  
  .. [1] Brett M. Averick et al. "The MINPACK-2 Test Problem Collection",
         p. 29
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code: def fun(self, x):
      return (
          x[0]
          * (self.u**2 + x[1] * self.u)
          / (self.u**2 + x[2] * self.u + x[3])
          - 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 EnzymeReaction obj's underlying member method code with example usage: obj.fun(x) and returns: unknown