code: def _build_parmlist(self, parameters):
          
  
          args = []
          for key, value in parameters.items():
              if not value is None:
                  # We always use the explicit-length keyname format, to reduce the chance
                  # of requests failing due to unusual characters in parameter values.
  
                  try:
                      classinfo = unicode
                  except NameError:
                      classinfo = str
  
                  if isinstance(value, classinfo):
                      key = '%s[%d]' % (key.upper(), len(value.encode('utf-8')))
                  else:
                      key = '%s[%d]' % (key.upper(), len(str(value)))
                  args.append('%s=%s' % (key, value))
          args.sort()
          parmlist = '&'.join(args)        
          return parmlist
docs: Converts a dictionary of name and value pairs into a 
          PARMLIST string value acceptable to the Payflow Pro API.