/*!
* @class LevelsPrefixRDConfig
*
* @headerfile <seqan/index.h>
*
* @brief LevelsPrefixRDConfig allows configuring a @link Levels @endlink
* RankDictionary that is recommended for fast searching in bidirectional
* indices.
*
* @signature template <typename TSize = size_t, typename TFibre = Alloc<>,
* unsigned LEVELS = 1, unsigned WORDS_PER_BLOCK = 0> struct
* LevelsRDConfig<TSize, TFibre, LEVELS, WORDS_PER_BLOCK>;
*
* @tparam TSize A data type that can store the length of the input text.
* Default: <tt>size_t</tt>
* @tparam TFibre A tag for specialization purposes of the underlying strings.
* Default: <tt>Alloc<></tt>
* @tparam LEVELS The number of levels (1, 2, or 3). The more levels, the lower
* the space consumption but possibly slight performance
* decreases. Default: <tt>1</tt>
* @tparam WORDS_PER_BLOCK The number of popcount operations per rank query. A
* lower number implies more space for faster runtime. 0
* is a shortcut for the size of the alphabet of the
* RankDictionary. Default: <tt>0</tt>
*/