class_docstr: TargetEncoder
code: def columns_to_encode(self, columns_to_encode):
      assert_is_type(columns_to_encode, None, [U(str, [str])])
      if columns_to_encode:  # standardize as a nested list
          columns_to_encode = [
              [g] if isinstance(g, str) else g
              for g in columns_to_encode
          ]
      self._parms["columns_to_encode"] = columns_to_encode
  
imports: from h2o.utils.metaclass import deprecated_params, deprecated_property
  import h2o
  import warnings
  from h2o.exceptions import H2ODeprecationWarning
  from h2o.utils.typechecks import U
  from h2o.estimators.estimator_base import H2OEstimator
  from h2o.exceptions import H2OValueError
  from h2o.frame import H2OFrame
  from h2o.utils.typechecks import assert_is_type, Enum, numeric
label_desc: Use image node_id 11 for calling the H2OTargetEncoderEstimator obj's underlying member method code with example usage: obj.columns_to_encode(columns_to_encode) without return types