public String getSubtypeWithoutSuffix() {
        int position = subtype.lastIndexOf('+');
        return position == -1 ? getSubtype() : subtype.substring(0, position);
    }
Gets the "subtype" of the media type with no structured syntax suffix.

<p>For example given, "application/foo+json", this method returns
"foo". Given "application/foo+baz+json", this method returns
"foo+baz".

@return Returns the subtype (e.g., "json", "foo+json").
smithy-utils/src/main/java/software/amazon/smithy/utils/MediaType.java