code: def all_survival_estimators():
      root = str(Path(sksurv.__file__).parent)
      all_classes = []
      for _importer, modname, _ispkg in pkgutil.walk_packages(
          path=[root], prefix="sksurv."
      ):
          # meta-estimators require base estimators
          if modname.startswith("sksurv.meta"):
              continue
          module = import_module(modname)
          for _name, cls in inspect.getmembers(
              module, _is_survival_mixin
          ):
              if inspect.isabstract(cls):
                  continue
              all_classes.append(cls)
      return set(all_classes)
  
file_path: scikit-survival/sksurv/testing.py
imports: from importlib import import_module
  import inspect
  from pathlib import Path
  import pkgutil
  import numpy
  from numpy.testing import assert_almost_equal, assert_array_equal
  import pytest
  import sksurv
  from sksurv.base import SurvivalAnalysisMixin
  from sksurv.metrics import concordance_index_censored
label_desc: Use image node_id 5 for calling a global function with example usage: all_survival_estimators() and returns: set