class_docstr: A PPA class, inherited from Optimizer.
  
  This is the designed class to define PPA-related
  variables and methods.
  
  References:
      A. Mohamed et al. Parasitism – Predation algorithm (PPA): A novel approach for feature selection.
      Ain Shams Engineering Journal (2020).
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code: def velocity(self, velocity: np.ndarray) -> None:
      if not isinstance(velocity, np.ndarray):
          raise e.TypeError("`velocity` should be a numpy array")
  
      self._velocity = velocity
  
imports: from typing import Any, Dict, Optional, Tuple
  import numpy
  import opytimizer.math.distribution
  import opytimizer.math.general
  import opytimizer.math.random
  import opytimizer.utils.exception
  from opytimizer.core import Optimizer
  from opytimizer.core.space import Space
  from opytimizer.utils import logging
label_desc: Use image node_id 3 for calling the PPA obj's underlying member method code with example usage: obj.velocity(velocity) without return types