Generates a SPARQL group graph pattern.
Empty clauses, such as those produced by nil, are dropped first; when none survives, the result is the empty fragment via nil, which callers must guard against where a pattern is required.
The graph pattern clauses to wrap
The braced SPARQL group pattern, or the empty fragment for no clauses
SPARQL 1.1 Group Graph Patterns
Generates a SPARQL group graph pattern.
Empty clauses, such as those produced by nil, are dropped first; when none survives, the result is the empty fragment via nil, which callers must guard against where a pattern is required.