SPARQL data fusion

from rdflib import Graph
g = Graph()
g.parse("data.ttl", format="turtle")

sparql = """
prefix sosa: <http://www.w3.org/ns/sosa/>
prefix dc: <http://purl.org/dc/elements/1.1/>

select ?secs1 ?secs2 ?label1 ?label2 ?diff where {
  [] a sosa:Observation;
    sosa:hasSimpleResult ?r1;
    sosa:madeBySensor ?s1 ;
    sosa:resultTime ?t1.
  ?s1 rdfs:label ?label1 .

  [] a sosa:Observation;
    sosa:hasSimpleResult ?r2;
    sosa:madeBySensor ?s2 ;
    sosa:resultTime ?t2.
  ?s2 rdfs:label ?label2 .

  FILTER(YEAR(?t1)=YEAR(?t2)) 
  FILTER(MONTH(?t1)=MONTH(?t2)) 
  FILTER(DAY(?t1)=DAY(?t2))

  BIND((HOURS(?t1)*60 + MINUTES(?t1))*60 + SECONDS(?t1) AS ?secs1)
  BIND((HOURS(?t2)*60 + MINUTES(?t2))*60 + SECONDS(?t2) AS ?secs2)
  BIND(?secs2 - ?secs1 AS ?diff)

  FILTER(0<?diff && ?diff<60)
}
"""
results = g.query(sparql)
print(str(results.serialize(format='csv'),'utf-8'))