Macro print_to_py 

macro_rules! print_to_py {
    ( $( $x:expr, $y:expr ),* ) => { ... };
    ( $x:expr ) => { ... };
}

For debugging purposes only! Given pairs of arbitrary keys and values, prints “key: value” to python intepreter.
Given str, prints str.
Using this will break cargo test but work with maturin develop.