class_docstr: A Node instance is used for composing tree-based structures.
class_docstr_tok: ["A","Node","instance","is","used","for","composing","tree-based","structures","."]
docstr: Number of nodes.
docstr_tok: ["Number","of","nodes","."]
code: def n_nodes(self) -> int:
      """Number of nodes."""
  
      return _properties(self)["n_nodes"]
  
imports: from __future__ import annotations
  from typing import Any, Dict, List, Optional, Union
  import numpy
  import opytimizer.utils.constant
  import opytimizer.utils.exception
label_desc: Use image node_id 21 for calling the Node obj's underlying member method code with example usage: obj.n_nodes() and returns: _properties