function is_text(content_type) {
	if (!content_type) return true; // defaults to json
	const type = content_type.split(';')[0].toLowerCase(); // get the mime type

	return type.startsWith('text/') || type.endsWith('+xml') || text_types.has(type);
}
Decides how the body should be parsed based on its mime type

@param {string | undefined | null} content_type The `content-type` header of a request/response.
@returns {boolean}