error: 'format' is not not a member of 'Boost::timer'

When I include and compile the code, the compile outputs the error " error: 'format' is not not a member of 'Boost::timer'". After I check the source code, the format functions are defined as:

1. std::string format(short places, const std::string& format) const { return ::boost::timer::format(elapsed(), places, format); }
2. std::string format(short places = default_places) const { return ::boost::timer::format(elapsed(), places); }

the function "::boost::timer::format(...)" within the format function actually does not exist in the code, anyone knows how to solve this problem?