parameters: (self, option, mvarfmt=' <%s>', optsep=', ')
return_statement: return ''.join(opts)
docstring: Return a comma-separated list of option strings and metavars.
  
          :param option:  tuple of (short opt, long opt), e.g: ('-f', '--format')
          :param mvarfmt: metavar format string - evaluated as mvarfmt % metavar
          :param optsep:  separator
docstring_summary: Return a comma-separated list of option strings and metavars.
docstring_tokens: Return a comma - separated list of option strings and metavars .
function: def _format_option_strings(self, option, mvarfmt=' <%s>', optsep=', '):
          """
          Return a comma-separated list of option strings and metavars.
  
          :param option:  tuple of (short opt, long opt), e.g: ('-f', '--format')
          :param mvarfmt: metavar format string - evaluated as mvarfmt % metavar
          :param optsep:  separator
          """
          opts = []
  
          if option._short_opts:
              opts.append(option._short_opts[0])
          if option._long_opts:
              opts.append(option._long_opts[0])
          if len(opts) > 1:
              opts.insert(1, optsep)
  
          if option.takes_value():
              metavar = option.metavar or option.dest.lower()
              opts.append(mvarfmt % metavar.lower())
  
          return ''.join(opts)
function_tokens: def _format_option_strings ( self , option , mvarfmt = ' <%s>' , optsep = ', ' ) : opts = [ ] if option . _short_opts : opts . append ( option . _short_opts [ 0 ] ) if option . _long_opts : opts . append ( option . _long_opts [ 0 ] ) if len ( opts ) > 1 : opts . insert ( 1 , optsep ) if option . takes_value ( ) : metavar = option . metavar or option . dest . lower ( ) opts . append ( mvarfmt % metavar . lower ( ) ) return '' . join ( opts )