class_docstr: Base forecaster template class.
  
  The base forecaster specifies the methods and method signatures that all forecasters
  have to implement.
  
  Specific implementations of these methods is deferred to concrete forecasters.
class_docstr_tok: ["Base","forecaster","template","class",".","The","base","forecaster","specifies","the","methods","and","method","signatures","that","all","forecasters","have","to","implement",".","Specific","implementations","of","these","methods","is","deferred","to","concrete","forecasters","."]
docstr: Shorthand for _check_X_y with one argument X, see _check_X_y.
docstr_tok: ["Shorthand","for","_check_X_y","with","one","argument","X",",","see","_check_X_y","."]
code: def _check_X(self, X=None):
      """Shorthand for _check_X_y with one argument X, see _check_X_y."""
      return self._check_X_y(X=X)[0]
  
imports: from copy import deepcopy
  from itertools import product
  import numpy
  import pandas
  from sktime.base import BaseEstimator
  from sktime.datatypes import VectorizedDF, check_is_scitype, convert_to, get_cutoff, mtype_to_scitype, scitype_to_mtype, update_data
  from sktime.forecasting.base._fh import ForecastingHorizon
  from sktime.utils.datetime import _shift
  from sktime.utils.validation._dependencies import _check_estimator_deps
  from sktime.utils.validation.forecasting import check_alpha, check_cv, check_fh, check_X
  from sktime.utils.validation.series import check_equal_time_index
  from sktime.utils.warnings import warn
label_desc: Use image node_id 21 for calling the BaseForecaster obj's underlying member method code with example usage: obj._check_X(X) and returns: self