new_contents: #!/usr/bin/env python3
  # -*- coding: utf-8 -*-
  
  __author__ = 'mookaka'
  
  import json, logging, inspect, functools
  
  
  class Page(object):
      '''
      Page object for display pages.
      '''
  
      def __init__(self, item_count, page_index=1, page_size=10):
          self.item_count = item_count
          self.page_size = page_size
          self.page_count = item_count // page_size + (1 if item_count % page_size > 0 else 0)
          if (item_count == 0) or (page_index > self.page_count):
              self.offset = 0
              self.limit = 0
              self.page_index = 1
          else:
              self.page_index = page_index
              self.offset = self.page_size * (page_index - 1)
              self.limit = self.page_size
  
          self.has_next = self.page_index < self.page_count
          self.has_previous = self.page_index > 1
  
      def __str__(self):
          return 'item_count: %s, page_count: %s, page_index: %s, page_size: %s, offset: %s, limit: %s' % (self.item_count, self.page_count, self.page_index, self.page_size, self.offset, self.limit)
  
      __repr__ = __str__
  
  
  class APIError(Exception):
      '''
      the base APIError which contains error(required), data(optional) and message(optional)
      '''
  
      def __init__(self, error, data='', message=''):
          super(APIError, self).__init__(message)
          self.error = error
          self.data = data
          self.message = message
  
  
  class APIValueError(APIError):
      '''
      Indicate the input value has error or invalid. The data specifies the error field of input form
      '''
  
      def __init__(self, field, message=''):
          super(APIValueError, self).__init__('value:invalid', field, message)
  
  
  class APIResourceNotFoundError(APIError):
      '''
      Indicate the resource was not found. The data specifies the resource name
      '''
  
      def __index__(self, field, message=''):
          super(APIResourceNotFoundError, self).__init__('resource:not found', field, message)
  
  
  class APIPermissionError(APIError):
      '''
      Indicate the api has no permission.
      '''
  
      def __init__(self, message=''):
          super(APIPermissionError, self).__init__('permission:forbidden', 'permission', message)
  
subject: add api.py which define the json data form and error type