new_contents: import json
  import sys
  import numpy as np
  from shapely.geometry import shape, Point
  
  f = open(sys.argv[1], 'r')
  js = json.load(f)
  f.close()
  
  tags = {}
  f = open(sys.argv[2], 'r')
  for line in f.readlines():
      tag = line.split(': ')
      tags[tag[0]] = tag[1][:-1]
  
  #for feature in js['features']:
  feature = js['features'][int(tags['parcelle_lineid'])]
  if feature['properties']['id'] != tags['parcelle_wayid']:
      print >> sys.stderr, "ERROR: wayid %s doesnot match with meta file (%s)" % (feature['properties']['id'], tags['parcelle_wayid'])
      sys.exit(1)
  for tag in tags.keys():
      feature['properties'][tag] = tags[tag]
          
  feature['geometry']['type'] = 'Polygon'
  feature['geometry']['coordinates'] = [feature['geometry']['coordinates']]
  
  js['features'] = [feature]
  
  print json.dumps(js);
  
subject: Create a geojson dedicated to the parcelle we are interested in