code: def write_to_file(self, filename):
          
          if not exists(dirname(filename)):
              return -1
          with open(filename, 'w') as fd:
              needs_json = json.dumps(self.minimum_needs)
              fd.write(needs_json)
          return 0
docs: Write minimum needs as json to a file.
  
          :param filename: The file to be written to.
          :type filename: basestring, str