docstr: Test Clear.
docstr_tok: ["Test","Clear","."]
code: def test_clear(self):
      """Test Clear."""
      self._api.SetImageFile(self._image_file)
      self._api.GetUTF8Text()
      self._api.Clear()
      self.assertRaises(RuntimeError, self._api.GetUTF8Text)
  
imports: import unittest
  import re
  import os.path
  import tesserocr
label_desc: Use image node_id 18 for calling the TestTessBaseApi obj's underlying member method code with example usage: obj.test_clear() without return types