class_docstr: Cosine transformation.
  
  This is a wrapper around numpy's cosine function (see :func:`numpy.cos`).
  
  See Also
  --------
  numpy.cos
  
  Examples
  --------
  >>> from sktime.transformations.series.cos import CosineTransformer
  >>> from sktime.datasets import load_airline
  >>> y = load_airline()
  >>> transformer = CosineTransformer()
  >>> y_hat = transformer.fit_transform(y)
docstr: Inverse transform X and return an inverse transformed version.
  
  core logic
  
  Parameters
  ----------
  X : 2D np.ndarray
      Data to be transformed
  y : ignored argument for interface compatibility
      Additional data, e.g., labels for transformation
  
  Returns
  -------
  Xt : 2D np.ndarray
      inverse transformed version of X
docstr_tok: ["Inverse","transform","X","and","return","an","inverse","transformed","version",".","core","logic","Parameters","--","--","--","--","--","X",":","2D","np.ndarray","Data","to","be","transformed","y",":","ignored","argument","for","interface","compatibility","Additional","data",",","e.g.",",","labels","for","transformation","Returns","--","--","--","-","Xt",":","2D","np.ndarray","inverse","transformed","version","of","X"]
code: def _inverse_transform(self, X, y=None):
      """Inverse transform X and return an inverse transformed version.
  
      core logic
  
      Parameters
      ----------
      X : 2D np.ndarray
          Data to be transformed
      y : ignored argument for interface compatibility
          Additional data, e.g., labels for transformation
  
      Returns
      -------
      Xt : 2D np.ndarray
          inverse transformed version of X
      """
      Xt = np.arccos(X)
      return Xt
  
imports: from math import pi
  import numpy
  from sktime.transformations.base import BaseTransformer
label_desc: Use image node_id 2 for calling the CosineTransformer obj's underlying member method code with example usage: obj._inverse_transform(X, y) and returns: Xt