void read(XMLReader& xml, const string& path, Prop_t& input)
void read(XMLReader& xml, const string& path, Propagator_input_t& input)
void read(XMLReader& xml, const string& path, Prop_t& input){  XMLReader inputtop(xml, path);//  read(inputtop, "source_file", input.source_file);  read(inputtop, "prop_file", input.prop_file);}