@Override
    public List<MultipartPart> getParts() {
        return parts;
    }
Constructs a new instance of {@code HttpRFC7578Multipart} with the given charset, boundary, and parts.

@param charset  the charset to use.
@param boundary the boundary string to use.
@param parts    the list of parts to include in the multipart message.
httpclient5/src/main/java/org/apache/hc/client5/http/entity/mime/HttpRFC7578Multipart.java