code: def load(self, json_file):
          
          cart_file = os.path.join(CART_LOCATION, json_file)
          try:
              cart_body = juicer.utils.read_json_document(cart_file)
          except IOError as e:
              juicer.utils.Log.log_error('an error occured while accessing %s:' %
                      cart_file)
              raise JuicerError(e.message)
  
          self.cart_name = cart_body['_id']
  
          if cart_body['current_env'] == '':
                  self.current_env = juicer.utils.get_login_info()[1]['start_in']
          else:
              self.current_env = cart_body['current_env']
  
          for repo, items in cart_body['repos_items'].iteritems():
              self.add_repo(repo, items)
docs: Build a cart from a json file