code: def merge(self, paths):
          
  
          # Use local topojson binary
          topojson_binary = 'node_modules/bin/topojson'
  
          if not os.path.exists(topojson_binary):
              # try with global topojson binary
              topojson_binary = 'topojson'
  
          merge_cmd = '%(binary)s -o %(output_path)s --bbox -p -- %(paths)s' % {
              'output_path': self.args.output_path,
              'paths': ' '.join(paths),
              'binary': topojson_binary
          }
  
          sys.stdout.write('Merging layers\n')
  
          if self.args.verbose:
              sys.stdout.write('  %s\n' % merge_cmd)
  
          r = envoy.run(merge_cmd)
  
          if r.status_code != 0:
              sys.stderr.write(r.std_err)
docs: Merge data layers into a single topojson file.