using from_Index function could lose columns for std::string

[Aperjump]

data_frame df2;
df2.from_tuples(std::vector{std::make_tuple(1, 3.3, "hello"), 
                                std::make_tuple(2, 2.2, "world"), 
                                std::make_tuple(3, 1.1, "bili")}, 
                    {"int_vec", "double_vec", "str_vec"});
df2.print_index<int, double, std::string>({0, 1, 2});

This will only print 2 columns and omit the std::string.

[Aperjump]

The problem is caused by type deduction. When calling make_tuple("hello") the type deduction for "hello" is const char*, but in print_index function we are passing std::string for induction, thta column cannot be found in type_map.
On solution is to use using namespace std::string_literals; and add s operator for each string literal
like

using namespace std::string_literals;
data_frame df2;
df2.from_tuples(std::vector{std::make_tuple(1, 3.3, "hello"s), 
                                std::make_tuple(2, 2.2, "world"s), 
                                std::make_tuple(3, 1.1, "bili"s)}, 
                    {"int_vec", "double_vec", "str_vec"});
df2.print_index<int, double, std::string>({0, 1, 2});