code: def __call__(self, params):
      return -0.5 * np.sum(params**2), self.blob_function(params)
  
file_path: emcee/src/emcee/tests/unit/test_blobs.py
imports: import warnings
  import numpy
  import pytest
  from emcee import EnsembleSampler, backends
label_desc: Use image node_id 2 for calling the BlobLogProb obj's underlying member method code with example usage: obj.__call__(params) and returns: unknown,  self