code: def test_init():
      fh = FileHolder("a_fname")
      assert fh.filename == "a_fname"
      assert fh.fileobj is None
      assert fh.pos == 0
      sio0 = BytesIO()
      fh = FileHolder("a_test", sio0)
      assert fh.filename == "a_test"
      assert fh.fileobj is sio0
      assert fh.pos == 0
      fh = FileHolder("a_test_2", sio0, 3)
      assert fh.filename == "a_test_2"
      assert fh.fileobj is sio0
      assert fh.pos == 3
  
imports: from io import BytesIO
  from ..fileholders import FileHolder
label_desc: Use image node_id 1 for calling a global function with example usage: test_init() without return types