class_docstr: A Space class for agents, variables and methods
  related to the search space.
class_docstr_tok: ["A","Space","class","for","agents",",","variables","and","methods","related","to","the","search","space","."]
docstr: Number of decision variables.
docstr_tok: ["Number","of","decision","variables","."]
code: def n_variables(self) -> int:
      """Number of decision variables."""
  
      return self._n_variables
  
imports: from typing import List, Optional, Tuple, Union
  import numpy
  import opytimizer.utils.exception
  from opytimizer.core import Agent
  from opytimizer.utils import logging
label_desc: Use image node_id 4 for calling the Space obj's underlying member method code with example usage: obj.n_variables() and returns: self