Returns true if the predicate holds for exactly one of the elements in the list.
Arguments:
list: An expression that returns a list.
variable: This is the variable that can be used from the predicate.
predicate: A predicate that is tested against all items in the list.
Example Query:
MATCH p=(n)-->(b)
WHERE n.name='Alice' AND SINGLE (var IN nodes(p) WHERE var.eyes = "blue")
RETURN p