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
  est : sktime.estimator, BaseEstimator descendant
      descriptive explanation of est
  est2: another estimator
      descriptive explanation of est2
  and so on
docstr: Fit transformer to X and y.
  
  private _fit containing the core logic, called from fit
  
  Parameters
  ----------
  X : Series or Panel of mtype X_inner_mtype
      if X_inner_mtype is list, _fit must support all types in it
      Data to fit transform to
  y : Series or Panel of mtype y_inner_mtype, default=None
      Additional data, e.g., labels for transformation
  
  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 : Series or Panel of mtype X_inner_mtype
          if X_inner_mtype is list, _fit must support all types in it
          Data to fit transform to
      y : Series or Panel of mtype y_inner_mtype, default=None
          Additional data, e.g., labels for transformation
  
      Returns
      -------
      self: reference to self
      """
  
file_path: sktime/extension_templates/transformer.py
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) without return types