docs: @Nonnull
    public Query whereEqualTo(@Nonnull FieldPath fieldPath, @Nullable Object value) {
      Preconditions.checkState(
          options.startCursor == null && options.endCursor == null,
          "Cannot call whereEqualTo() after defining a boundary with startAt(), "
              + "startAfter(), endBefore() or endAt().");
      QueryOptions newOptions = new QueryOptions(options);
  
      if (isUnaryComparison(value)) {
        newOptions.fieldFilters.add(new UnaryFilter(fieldPath, value));
      } else {
        if (fieldPath.equals(FieldPath.DOCUMENT_ID)) {
          value = this.convertReference(value);
        }
        newOptions.fieldFilters.add(new ComparisonFilter(fieldPath, EQUAL, value));
      }
  
      return new Query(firestore, path, newOptions);
    }