code: def step(self, model: Model, sigma: Sigma) -> float:
      sample_value = self.sample(model, sigma)
      sigma.set_value(sample_value)
      return sample_value
  
file_path: imodels/imodels/experimental/bartpy/samplers/sigma.py
imports: import numpy
  from ..model import Model
  from ..samplers.sampler import Sampler
  from ..sigma import Sigma
label_desc: Use image node_id 1 for calling the SigmaSampler obj's underlying member method code with example usage: obj.step(model, sigma) and returns: sample_value