code: func (s *Schema) String() string {
  	colStrs := make([]string, 0, len(s.Columns))
  	for _, col := range s.Columns {
  		colStrs = append(colStrs, col.String())
  	}
  	ukStrs := make([]string, 0, len(s.Keys))
  	for _, key := range s.Keys {
  		ukColStrs := make([]string, 0, len(key))
  		for _, col := range key {
  			ukColStrs = append(ukColStrs, col.String())
  		}
  		ukStrs = append(ukStrs, "["+strings.Join(ukColStrs, ",")+"]")
  	}
  	return "Column: [" + strings.Join(colStrs, ",") + "] Unique key: [" + strings.Join(ukStrs, ",") + "]"
  }
docs: // String implements fmt.Stringer interface.