code: @SuppressWarnings({"WeakerAccess", "unused", "SameParameterValue"}) // For library users
      @Nullable
      public List<String> getFacetRefinements(@NonNull String attribute) {
          return refinementMap.get(attribute);
      }
docs: Gets the refinement values for a faceted attribute.
  
  @param attribute the attribute refined on.
  @return the refinements enabled for the given attribute, or {@code null} if there is none.