code: def K(
      self, X: TensorType, X2: Optional[TensorType] = None
  ) -> tf.Tensor:
      return self._reduce([k.K(X, X2) for k in self.kernels])
  
imports: import abc
  from functools import partial, reduce
  from typing import Callable, List, Optional, Sequence, Tuple, Union, overload
  import numpy
  import tensorflow
  from check_shapes import check_shapes
  from ..base import AnyNDArray, Module, TensorType
label_desc: Use image node_id 2 for calling the ReducingCombination obj's underlying member method code with example usage: obj.K(X, X2) and returns: self