Trying to extract BLAST results into xml outfile from larger BLAST xml file

This is probably a fairly basic question, so I apologize in advance, but I can't seem to figure out how to output xml format using Biopython. Basically, I have a fairly large BLAST results file in xml format and I'm trying to extract a portion of that file using a list of specific queries I am interest in. I can find the queries in the larger file, but I can't seem to output them into xml format. Here is the script I am currently using:

#!/usr/bin/env python

import sys
import os
import sets
import Bio
from sets import Set
from Bio.Blast import NCBIXML

# Usage.
if len(sys.argv) < 2:
        print ""
        print "This program extracts blast results from an xml file given a list of query sequences"
        print "Usage: %s -list file1 -xml file2 -out file3"
        print "-list: list of sequence names"
        print "-xml: fasta file"
        print "-out: outfile name"
        print ""
        sys.exit()

# Parse args.
for i in range(len(sys.argv)):
        if sys.argv[i] == "-list":
                infile1 = sys.argv[i+1]
        elif sys.argv[i] == "-xml":
                infile2 = sys.argv[i+1]
        elif sys.argv[i] == "-out":
                outfile = sys.argv[i+1]

fls = [infile1,infile2,outfile]
results_handle = open(fls[1], "r")
fin1 = open(fls[0],"r")
save_file = open(fls[2], "w")
geneContigs = Set([])
results_list = list()
blast_records = NCBIXML.parse(results_handle)

for line in fin1:
    temp=line.lstrip('>').split()
    geneContigs.add(temp[0])
fin1.close()

for blast_record in blast_records:
        if(blast_record.query in geneContigs):
                save_file.write(blast_record)
save_file.close()

When I do this, I get the following error:

TypeError: argument 1 must be string or read-only character buffer, not Blast

Anyone have any suggestions on how to turn this Blast record into a string in xml output format?

Thanks