initialize the object of a InMemoryUploadedFile class with arguments: file set to self.file, field_name set to self.field_name,
return InMemoryUploadedFile ( file = self . file , field_name = self . field_name , name = self . file_name , content_type = self . content_type , size = file_size , charset = self . charset , content_type_extra = self . content_type_extra )