code: @SuppressWarnings("unchecked")
      static <T> Collection<T> asCollection(Object value, PDescriptor itemType) throws ProvidenceConfigException {
          if (value instanceof Collection) {
              Collection<T> out = new ArrayList<>();
              for (Object item : (Collection) value) {
                  out.add((T) asType(itemType, item));
              }
              return out;
          }
          throw new ProvidenceConfigException(
                  "Unable to convert " + value.getClass().getSimpleName() + " to a collection");
      }
docs: Convert the value to a collection.
  
  @param value The value instance.
  @param itemType The item type descriptor.
  @param <T> The item type.
  @return The collection value.
  @throws ProvidenceConfigException When unable to convert value.