$subVar
$subVar :
Description of hasParameter
isVariable(string $variable)
Checks it a given string is a valid SPARQL variable name (see https://www.w3.org/TR/2013/REC-sparql11-query-20130321/#rVARNAME)
Current implementation is more restrictive that the SPARQL standard as Unicode ranges #x00B7, #x0300-#x036F, #x203F-#x2040, #x00C0-#x00D6,
string | $variable | SPARQL variable name to match |