code: def encode_items(items):
      
      encoded = []
      for key, values in items:
          for value in values:
              encoded.append((key.encode('utf-8'), value.encode('utf-8')))
      return encoded
docs: Function that encode all elements in the list of items passed as
      a parameter
  
      :param items:  A list of tuple
      :returns:      A list of tuple with all items encoded in 'utf-8'