code: def test_common_four_gram(self):
      assert fn.commonFourGram("don4ld") == {"don4", "on4l", "n4ld"}
      assert fn.commonFourGram("donald 1992") == {
          "dona",
          "onal",
          "nald",
          "ald1",
          "ld19",
          "d199",
          "1992",
      }
      assert fn.commonFourGram("g00fy  ") == {"g00f", "00fy"}
      assert fn.commonFourGram(" c1p   c10p ") == {
          "c1pc",
          "1pc1",
          "pc10",
          "c10p",
      }
  
imports: import unittest
  from dedupe import predicate_functions
  from dedupe.cpredicates import ngrams
label_desc: Use image node_id 16 for calling the TestPredicateFunctions obj's underlying member method code with example usage: obj.test_common_four_gram() without return types