_prepare = (schema) => {
  const preparedString = JSON.stringify(schema, (_, value) => {
    if (!value.isSJS) return value;
    return `${value.type}__sjs`;
  });

  const preparedSchema = JSON.parse(preparedString);

  return {
    preparedString,
    preparedSchema,
  };
}
`_prepare` - aims to normalize the schema provided by the user.
It will convert the schema in both a parseable string and an object
useable for making the chunks needed for the serialization part.
@param {object} schema - user provided schema