docstr: The number of performed alternate tree swaps.
  
  Not applicable if the warning detectors are disabled.
code: def n_tree_swaps(self) -> collections.Counter:
      """The number of performed alternate tree swaps.
  
      Not applicable if the warning detectors are disabled.
      """
      return self._n_tree_swaps
  
imports: from __future__ import annotations
  import abc
  import collections
  import math
  import random
  import sys
  from river import base, drift, metrics, tree, utils
  from river.tree.nodes.et_nodes import ETLeafAdaptive, ETLeafMean, ETLeafModel
  from river.tree.splitter.random_splitter import RegRandomSplitter
label_desc: Use image node_id 15 for calling the ExtraTrees obj's underlying member method code with example usage: obj.n_tree_swaps() and returns: self