clean

Write a function clean that when is given a string and returns the string with the leading and

trailing space characters removed. Details:

you must use while loop$($s$)$

you must not use the strip method

the space characters are the space $,$ newline $\text{'}\frac{?}{?}$

${?}^{\text{'}}\text{'},$ and tab $\text{'}\frac{\frac{?}{?}}{t}\text{'}$