code: def default_headers(self):
          
          _headers = {
              "User-Agent": "Pyzotero/%s" % __version__,
              "Zotero-API-Version": "%s" % __api_version__,
          }
          if self.api_key:
              _headers["Authorization"] = "Bearer %s" % self.api_key
          return _headers
docs: It's always OK to include these headers