code: def assert_alldead(refs):
      for ref in refs:
          assert ref() is None
  
file_path: pyqtgraph/tests/test_ref_cycles.py
imports: import warnings
  import weakref
  import numpy
  import pyqtgraph
label_desc: Use image node_id 1 for calling a global function with example usage: assert_alldead(refs) without return types