code: public function getSchemaNames($refresh = false)
      {
          if ($this->_schemaNames === null || $refresh) {
              $this->_schemaNames = $this->findSchemaNames();
          }
  
          return $this->_schemaNames;
      }
docs: Returns all schema names in the database, except system schemas.
  @param bool $refresh whether to fetch the latest available schema names. If this is false,
  schema names fetched previously (if available) will be returned.
  @return string[] all schema names in the database, except system schemas.
  @since 2.0.4