class_docstr: Custom transformer. todo: write docstring.
  
  todo: describe your custom transformer here
      fill in sections appropriately
      docstring must be numpydoc compliant
  
  Parameters
  ----------
  parama : int
      descriptive explanation of parama
  paramb : string, optional (default='default')
      descriptive explanation of paramb
  paramc : boolean, optional (default= whether paramb is not the default)
      descriptive explanation of paramc
  and so on
docstr: Fit transformer to X and y.
  
  private _fit containing the core logic, called from fit
  
  Parameters
  ----------
  X : pd.DataFrame
      if self.get_tag("univariate-only")==True:
          guaranteed to have a single column
      if self.get_tag("univariate-only")==False: no restrictions apply
  y : None, present only for interface compatibility
  
  Returns
  -------
  self: reference to self
docstr_tok: ["Fit","transformer","to","X","and","y.","private","_fit","containing","the","core","logic",",","called","from","fit","Parameters","--","--","--","--","--","X",":","pd.DataFrame","if","self.get_tag","(","``","univariate-only","''",")","==True",":","guaranteed","to","have","a","single","column","if","self.get_tag","(","``","univariate-only","''",")","==False",":","no","restrictions","apply","y",":","None",",","present","only","for","interface","compatibility","Returns","--","--","--","-","self",":","reference","to","self"]
code: def _fit(self, X, y=None):
      """Fit transformer to X and y.
  
      private _fit containing the core logic, called from fit
  
      Parameters
      ----------
      X : pd.DataFrame
          if self.get_tag("univariate-only")==True:
              guaranteed to have a single column
          if self.get_tag("univariate-only")==False: no restrictions apply
      y : None, present only for interface compatibility
  
      Returns
      -------
      self: reference to self
      """
      # any model parameters should be written to attributes ending in "_"
      #  attributes set by the constructor must not be overwritten
      #
      # todo:
      # insert logic here
      # self.fitted_model_param_ = sthsth
      #
      return self
  
imports: from sktime.transformations.base import BaseTransformer
label_desc: Use image node_id 2 for calling the MyTransformer obj's underlying member method code with example usage: obj._fit(X, y) and returns: self