original_string: protected function _convertOnClause($clause)
      {
          if ($clause === 'CASCADE' || $clause === 'RESTRICT') {
              return strtolower($clause);
          }
          if ($clause === 'NO ACTION') {
              return TableSchema::ACTION_NO_ACTION;
          }
  
          return TableSchema::ACTION_SET_NULL;
      }
code: protected function _convertOnClause($clause)
      {
          if ($clause === 'CASCADE' || $clause === 'RESTRICT') {
              return strtolower($clause);
          }
          if ($clause === 'NO ACTION') {
              return TableSchema::ACTION_NO_ACTION;
          }
  
          return TableSchema::ACTION_SET_NULL;
      }
code_tokens: protected function _convertOnClause ( $ clause ) { if ( $ clause === 'CASCADE' || $ clause === 'RESTRICT' ) { return strtolower ( $ clause ) ; } if ( $ clause === 'NO ACTION' ) { return TableSchema :: ACTION_NO_ACTION ; } return TableSchema :: ACTION_SET_NULL ; }
docstring: Convert string on clauses to the abstract ones.
  
  @param string $clause The on clause to convert.
  @return string|null
docstring_tokens: Convert string on clauses to the abstract ones .