code: def _not_converged(y_truth, y_prediction, tol=1e-3):
      """basic convergence check"""
      return np.abs(y_truth - y_prediction).sum() > tol
  
imports: from abc import ABCMeta, abstractmethod
  import numpy
  from scipy import sparse
  from ..base import BaseEstimator, ClassifierMixin
  from ..externals import six
  from ..metrics.pairwise import rbf_kernel
  from ..neighbors.unsupervised import NearestNeighbors
  from ..utils.extmath import safe_sparse_dot
  from ..utils.graph import graph_laplacian
  from ..utils.multiclass import check_classification_targets
  from ..utils.validation import check_X_y, check_is_fitted, check_array
label_desc: Use image node_id 1 for calling a global function with example usage: _not_converged(y_truth, y_prediction, tol) and returns: unknown