code: def listMetaContentTypes(self):
          
  
          all_md_content_types = (
              CT_CORE_PROPS,
              CT_EXT_PROPS,
              CT_CUSTOM_PROPS)
          return [k for k in self.overrides.keys() if k in all_md_content_types]
docs: The content types with metadata
          @return: ['application/xxx', ...]