human
Solve the following python programming problem given the following code:
@ requires_os_link 
def test_copy_file_hard_link_failure(self) : 
    with open (self.source, 'w') as f : 
        f.write ('some content') 
st = os.stat (self.source) 
    def _os_link(* args) : 
        raise OSError (0, 'linking unsupported') 
old_link = os.link 
    os.link = _os_link 
    try : 
        copy_file (st.source, self.target, link = 'hard') 
finally : 
        os.link = old_link 
st2 = os.stat (self.source) 
    st3 = os.stat (self.target) 
    self.assertTrue (os.path.samestat (st, st2), (st, st2)) 
    self.assertFalse (os.path.samestat (st2, st3), (st2, st3)) 
    for fn in (self.source, self.target) : 
        with open (fn, 'r') as f : 
            self.assertEqual (f.read (), 'some content') 

    
    

    Fix the buggy line: copy_file (st.source, self.target, link = 'hard')
assistant
#Here is Python code to fix the buggy line: copy_file (st.

copy_file (self.source, self.target, link = 'hard')