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Succeeds if Key is a key in the map and unify Answer with the
number of values associated with the key. This provides a fast
test of existence without fetching the possibly large
associated value set as with rdf_find_literal_map/3.
Unify Answer with an ordered set of all keys that have the
given prefix. See section 3.1 for details on prefix matching.
Prefix must be an atom. This call is intended for
auto-completion in user interfaces.
Unify Answer with all keys that are larger or equal to the
Unify Answer with all keys that are smaller or equal to the integer
between(+Min, +Max) Unify
Answer with all keys between Min and Max (including).