docs: def _migrateStorageSchema(self, metadata: MetaData) -> None:
          """ Initialise the DB
  
          This method is called by the platform between the load() and start() calls.
          There should be no need for a plugin to call this method it's self.
  
          :param metadata: the SQLAlchemy metadata for this plugins schema
  
          """
  
          relDir = self._packageCfg.config.storage.alembicDir(require_string)
          alembicDir = os.path.join(self.rootDir, relDir)
          if not os.path.isdir(alembicDir): raise NotADirectoryError(alembicDir)
  
          self._dbConn = DbConnection(
              dbConnectString=self.platform.dbConnectString,
              metadata=metadata,
              alembicDir=alembicDir,
              enableCreateAll=False
          )
  
          self._dbConn.migrate()