code: def _ed1(token):
      
      insertion = {letter.join([token[:i], token[i:]]) for letter in string.ascii_lowercase for i in range(1, len(token) + 1)}
      deletion = {''.join([token[:i], token[i+1:]]) for i in range(1, len(token) + 1)}
      substitution = {letter.join([token[:i], token[i+1:]]) for letter in string.ascii_lowercase for i in range(1, len(token) + 1)}
      transposition = {''.join([token[:i], token[i+1:i+2],  token[i:i+1], token[i+2:]]) for i in range(1, len(token)-1)}
      return set.union(insertion, deletion, substitution, transposition)
docs: Return tokens the edit distance of which is one from the given token