code: def one(iterable, cmp=None):
      
      the_one = False
      for i in iterable:
          if cmp(i) if cmp else i:
              if the_one:
                  return False
              the_one = i
      return the_one
docs: Return the object in the given iterable that evaluates to True.
  
      If the given iterable has more than one object that evaluates to True,
      or if there is no object that fulfills such condition, return False.
  
      If a callable ``cmp`` is given, it's used to evaluate each element.
  
  
          >>> one((True, False, False))
          True
          >>> one((True, False, True))
          False
          >>> one((0, 0, 'a'))
          'a'
          >>> one((0, False, None))
          False
          >>> one((True, True))
          False
          >>> bool(one(('', 1)))
          True
          >>> one((10, 20, 30, 42), lambda i: i > 40)
          42