code: public static Collection<AbstractAttribute> findAllAttributes(
              final boolean parallel, final AbstractHtml... fromTags)
              throws NullValueException {
  
          if (fromTags == null) {
              throw new NullValueException("fromTags cannot be null");
          }
  
          final Collection<Lock> locks = getReadLocks(fromTags);
          for (final Lock lock : locks) {
              lock.lock();
          }
          try {
              return getAllNestedChildrenIncludingParent(parallel, fromTags)
                      .filter(tag -> tag.getAttributes() != null).map(tag -> {
                          return tag.getAttributes();
                      }).flatMap(attributes -> attributes.stream())
                      .collect(Collectors.toSet());
          } finally {
              for (final Lock lock : locks) {
                  lock.unlock();
              }
          }
      }
docs: Finds all attributes from the given tags
  
  @param parallel
  true to internally use parallel stream. If true it
  will split the finding task to different batches and
  will execute the batches in different threads in
  parallel consuming all CPUs. It will perform faster
  in finding from extremely large number of tags but at
  the same time it will less efficient in finding from
  small number of tags.
  @param fromTags
  the tags to find the attributes from.
  @return the all attributes from the given tags including the nested tags.
  @throws NullValueException
  if {@code fromTags} is null
  @since 3.0.0
  @author WFF