docs: def prepare_video_params(self, title=None, tags='Others', description='',
                               copyright_type='original', public_type='all',
                               category=None, watch_password=None,
                               latitude=None, longitude=None, shoot_time=None
                               ):
          """ util method for create video params to upload.
  
          Only need to provide a minimum of two essential parameters:
          title and tags, other video params are optional. All params spec
          see: http://cloud.youku.com/docs?id=110#create .
  
          Args:
              title: string, 2-50 characters.
              tags: string, 1-10 tags joind with comma.
              description: string, less than 2000 characters.
              copyright_type: string, 'original' or 'reproduced'
              public_type: string, 'all' or 'friend' or 'password'
              watch_password: string, if public_type is password.
              latitude: double.
              longitude: double.
              shoot_time: datetime.
  
          Returns:
              dict params that upload/create method need.
          """
          params = {}
          if title is None:
              title = self.file_name
          elif len(title) > 80:
              title = title[:80]
  
          if len(description) > 2000:
              description = description[0:2000]
  
          params['title'] = title
          params['tags'] = tags
          params['description'] = description
          params['copyright_type'] = copyright_type
          params['public_type'] = public_type
          if category:
              params['category'] = category
          if watch_password:
              params['watch_password'] = watch_password
          if latitude:
              params['latitude'] = latitude
          if longitude:
              params['longitude'] = longitude
          if shoot_time:
              params['shoot_time'] = shoot_time
  
          return params