(req)
return ':' + str(req.marker) if req.marker else ''
For a requirement, return the 'extras_require' suffix for
        that requirement.
For a requirement, return the 'extras_require' suffix for
        that requirement.
For a requirement return the extras_require suffix for that requirement .
def _suffix_for(req):
        """
        For a requirement, return the 'extras_require' suffix for
        that requirement.
        """
        return ':' + str(req.marker) if req.marker else ''
def _suffix_for ( req ) : return ':' + str ( req . marker ) if req . marker else ''