class_docstr: Abstract class for Explore in :py:class:`orion.algo.pbt.pbt.PBT`
  
  The explore class is responsible for proposing new parameters for a given trial and space.
  
  This class is expected to be stateless and serve as a configurable callable object.
docstr: Execute explore
  
  The method receives the space and the parameters of the current trial under examination.
  It must then select new parameters for the trial.
  
  Parameters
  ----------
  rng: numpy.random.Generator
      A random number generator. It is not contained in ``BaseExplore`` because the explore
      class must be stateless.
  space: Space
      The search space optimized by the algorithm.
  params: dict
      Dictionary representing the parameters of the current trial under examination
      (`trial.params`).
  
  Returns
  -------
  ``dict``
      The new set of parameters for the trial to be branched.
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code: def __call__(self, rng, space, params):
      """Execute explore
  
      The method receives the space and the parameters of the current trial under examination.
      It must then select new parameters for the trial.
  
      Parameters
      ----------
      rng: numpy.random.Generator
          A random number generator. It is not contained in ``BaseExplore`` because the explore
          class must be stateless.
      space: Space
          The search space optimized by the algorithm.
      params: dict
          Dictionary representing the parameters of the current trial under examination
          (`trial.params`).
  
      Returns
      -------
      ``dict``
          The new set of parameters for the trial to be branched.
  
      """
  
imports: import numpy
  from orion.core.utils import GenericFactory
  from orion.core.utils.flatten import flatten, unflatten
label_desc: Use image node_id 2 for calling the BaseExplore obj's underlying member method code with example usage: obj.__call__(rng, space, params) without return types