class_docstr: Truncate unequal length panels to lower/upper bounds.
  
  Truncates all series in panel between lower/upper range bounds.
  
  Parameters
  ----------
  lower : int, optional (default=None) bottom range of the values to
              truncate can also be used to truncate to a specific length
              if None, will find the shortest sequence and use instead.
  upper : int, optional (default=None) upper range, only required when
              paired with lower.
              This is used to calculate the range between. exclusive.
              if None, will truncate from 0 to the lower bound.
docstr: Fit transformer to X and y.
  
  private _fit containing the core logic, called from fit
  
  Parameters
  ----------
  X : nested pandas DataFrame of shape [n_instances, n_features]
      each cell of X must contain pandas.Series
      Data to fit transform to
  y : ignored argument for interface compatibility
      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 : nested pandas DataFrame of shape [n_instances, n_features]
          each cell of X must contain pandas.Series
          Data to fit transform to
      y : ignored argument for interface compatibility
          Additional data, e.g., labels for transformation
  
      Returns
      -------
      self : reference to self
      """
      if self.lower is None:
          n_instances, _ = X.shape
          arr = [X.iloc[i, :].values for i in range(n_instances)]
          self.lower_ = self._get_min_length(arr)
      else:
          self.lower_ = self.lower
  
      return self
  
file_path: sktime/sktime/transformations/panel/truncation.py
imports: import numpy
  import pandas
  from sktime.transformations.base import BaseTransformer
label_desc: Use image node_id 3 for calling the TruncationTransformer obj's underlying member method code with example usage: obj._fit(X, y) and returns: self