code: def test_combined_cutoff_top(self):
      expected = self.df.loc[:, ["C"]]
      result = msno.nullity_filter(self.df, n=2, p=0.7, filter="top")
      assert result.equals(expected)
  
imports: import unittest
  import pandas
  import numpy
  import sys
  import missingno
label_desc: Use image node_id 7 for calling the TestNullityFilter obj's underlying member method code with example usage: obj.test_combined_cutoff_top() without return types