Creates an string representation of the UrlTrustedSigners object
            by overriding the default Object ToString method. This string
            can be concatenated to the distribution config xml that is sent 
            to CloudFront while creating a distribution or updating a distribution's
            configuration.
            
 Declaration Syntax
 Declaration Syntax| C# | 
public override string ToString()
 Return Value
 Return Value
            String representation of the UrlTrustedSigners type.