code: def min(self, key=None):
          
          if key is None:
              return self.reduce(min)
          return self.reduce(lambda a, b: min(a, b, key=key))
docs: Find the minimum item in this RDD.
  
          :param key: A function used to generate key for comparing
  
          >>> rdd = sc.parallelize([2.0, 5.0, 43.0, 10.0])
          >>> rdd.min()
          2.0
          >>> rdd.min(key=str)
          10.0