private String queryString(String name, List<String> values) {
    if (this.pure) {
      return name;
    }

    if (!values.isEmpty()) {
      return this.collectionFormat.join(name, values, StandardCharsets.UTF_8).toString();
    }

    /* nothing to return, all values are unresolved */
    return null;
  }
Expand this template. Unresolved variables are removed. If all values remain unresolved, the
result is an empty string.

@param variables containing the values for expansion.
@return the expanded template.
core/src/main/java/feign/template/QueryTemplate.java