input: Write a function to determine if two strings are equal, different, or similar up to a provided threshold using a Python class. If the strings are equal, return True; if they are different, return False; if they are similar up to the threshold, return True. If either of the strings is empty, return False.
  
  class StringComparator:
  
   def __init__(self, string1, string2):
    self.string1 = string1
    self.string2 = string2
  
   def is_equal(self):
    return self.string1 == self.string2
  
   def is_different(self):
    return self.string1 != self.string2
  
   def is_similar(self, threshold=0.5):
    distance = edit_distance(self.string1, self.string2)
    max_length = max(len(self.string1), len(self.string2))
  
    return distance / max_length < threshold
  
  assert StringComparator("abc", "abc").is_equal()==True
  assert StringComparator("abc", "xyz").is_different()==True
  assert StringComparator("abc", "abcd").is_similar(threshold=0.25)==True
  assert StringComparator("abc", "ab").is_similar(threshold=0.5)==False
  assert StringComparator("empty", "").is_different()==True
output: def is_similar(self, threshold=0.5):
      if not self.string1 or not self.string2:
          return False
      distance = edit_distance(self.string1, self.string2)
      max_length = max(len(self.string1), len(self.string2))
      return distance / max_length < threshold