code: def credentials(self):
          
          if self.filename:
              db_filename = os.path.join(os.getcwd(), self.filename)
          else:
              db_filename = None
  
          return {
              "username": self.username,
              "password": self.password,
              "hostname": self.hostname,
              "port": self.port,
              "filename": db_filename,
              "dbname": self.dbname,
              "dbtype": self.dbtype,
              "schemas": self.schemas,
              "limit": self.limit,
              "keys_per_column": self.keys_per_column,
          }
docs: Dict representation of all credentials for the database.