class_docstr: This class is responsible for loading tests according to various criteria
  and returning them wrapped in a TestSuite
code: def __init__(self):
      super(TestLoader, self).__init__()
      self.errors = []
      # Tracks packages which we have called into via load_tests, to
      # avoid infinite re-entrancy.
      self._loading_packages = set()
  
imports: import os
  import re
  import sys
  import traceback
  import types
  import functools
  import warnings
  from fnmatch import fnmatch, fnmatchcase
  from .None import case, suite, util
label_desc: Use image node_id 1 to create a new TestLoader object from inherited base classes: object with example: obj = TestLoader()