Write a function in python called num$\_$halves that takes a positive number as input, and that uses a while$-$loop to count and return the number of times we need to halve the number before it becomes smaller than $0\mathrm{.}1.$

For example, starting with the number $20,$ we get

$20-$:$2=10$

$10-$:$2=5$

$5-$:$2=2\mathrm{.}5$

$2\mathrm{.}5-$:$2=1\mathrm{.}25$

$1\mathrm{.}25-$:$2=0\mathrm{.}625$

$0\mathrm{.}625-$:$2=0\mathrm{.}3125$

$0\mathrm{.}3125-$:$2=0\mathrm{.}15625$

$0\mathrm{.}15625-$:$2=0\mathrm{.}078125$

That took $8$ halvings to get below $0\mathrm{.}1,$ so calling num$\_$halves$(20)$ should return $8.$