code: func (m *symbol) string() string {
  	var result string
  
  	for _, row := range m.module {
  		for _, value := range row {
  			switch value {
  			case true:
  				result += "  "
  			case false:
  				// Unicode 'FULL BLOCK' (U+2588).
  				result += "██"
  			}
  		}
  		result += "\n"
  	}
  
  	return result
  }
docs: // string returns a pictorial representation of the symbol, suitable for
  // printing in a TTY.