code: def is_one_edit(s, t):
      
      if len(s) > len(t):
          return is_one_edit(t, s)
      if len(t) - len(s) > 1 or t == s:
          return False
      for i in range(len(s)):
          if s[i] != t[i]:
              return s[i+1:] == t[i+1:] or s[i:] == t[i+1:]
      return True
docs: :type s: str
      :type t: str
      :rtype: bool