class_docstr: Mixin class to allow for a Box-Cox transformation.
docstr: Back-transforms the Box-Cox transformed data array, by means of the
  indicated method. The provided argument lmbda should be the lambda
  parameter that was used to initially transform the data.
  
  Parameters
  ----------
  x : array_like
      The transformed series.
  lmbda : float
      The lambda parameter that was used to transform the series.
  method : {'naive'}
      Indicates the method to be used in the untransformation. Defaults
      to 'naive', which reverses the transformation.
  
      NOTE: 'naive' is implemented natively, while other methods may be
      available in subclasses!
  
  Returns
  -------
  y : array_like
      The untransformed series.
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code: def untransform_boxcox(self, x, lmbda, method="naive"):
      """
      Back-transforms the Box-Cox transformed data array, by means of the
      indicated method. The provided argument lmbda should be the lambda
      parameter that was used to initially transform the data.
  
      Parameters
      ----------
      x : array_like
          The transformed series.
      lmbda : float
          The lambda parameter that was used to transform the series.
      method : {'naive'}
          Indicates the method to be used in the untransformation. Defaults
          to 'naive', which reverses the transformation.
  
          NOTE: 'naive' is implemented natively, while other methods may be
          available in subclasses!
  
      Returns
      -------
      y : array_like
          The untransformed series.
      """
      method = method.lower()
      x = np.asarray(x)
  
      if method == "naive":
          if np.isclose(lmbda, 0.0):
              y = np.exp(x)
          else:
              y = np.power(lmbda * x + 1, 1.0 / lmbda)
      else:
          raise ValueError(f"Method '{method}' not understood.")
  
      return y
  
file_path: statsmodels/statsmodels/base/transform.py
imports: import numpy
  from statsmodels.robust import mad
  from scipy.optimize import minimize_scalar
label_desc: Use image node_id 2 for calling the BoxCox obj's underlying member method code with example usage: obj.untransform_boxcox(x, lmbda, method) and returns: y