如何在rdflib中获取sparql查询中的标记位置

from rdflib import Graph, Literal, BNode, RDF
from rdflib.namespace import FOAF, XSD, Namespace
from rdflib.plugins.sparql import prepareQuery

graph = Graph()

graph.add((FOAF.Person, RDF.type, FOAF.Class))
graph.add((FOAF.Person, FOAF.name, Literal("Alice")))
graph.add((FOAF.Person, FOAF.age, Literal(25, datatype=XSD.integer)))

sparql_query = """
    PREFIX foaf: <http://xmlns.com/foaf/0.1/>
    SELECT ?person ?name ?age
    WHERE {
        ?person rdf:type foaf:Person .
        ?person foaf:name ?name .
        ?person foaf:age ?age .
    }
"""

query = prepareQuery(sparql_query, initNs={"foaf": FOAF})

result = graph.query(query)

for row in result:
    print(f"Person: {row.person}")
    print(f"Name: {row.name}")
    print(f"Age: {row.age}")
    print("------------")