code: func ValidCharsetAndCollation(cs string, co string) bool {
  	// We will use utf8 as a default charset.
  	if cs == "" {
  		cs = "utf8"
  	}
  
  	c, ok := charsets[cs]
  	if !ok {
  		return false
  	}
  
  	if co == "" {
  		return true
  	}
  	_, ok = c.Collations[co]
  	if !ok {
  		return false
  	}
  
  	return true
  }
docs: // ValidCharsetAndCollation checks the charset and the collation validity
  // and returns a boolean.