Problem PQ$5.$ Writing Object$-$Oriented Python Code.

$($a$)[15$ points$]$ Complete the code below for an Element class.

$$ It will have attributes for symbol, atomic number, and atomic weight. For example,

helium has symbol He$,$ atomic number $2,$ and atomic weight $4\mathrm{.}003.$

$$ Write a $3-$parameter constructor init that can be used to set all three attributes,

with default attribute values of $"",0,$ and $0\mathrm{.}0,$ respectively.

$$ Write getter and setter instance methods for the atomic number only.

class Element:

$($b$)[5$ points$]$ Add Python statements to create an application program below that $($i$)$ creates

and initializes the Element object helium using your constructor and all three of its actual

attribute values $($listed above$)$; $($ii$)$ creates an list of objects that could be used for all $118$

elements of the periodic table, but with only the atomic number initialized to a non$-$default

value.

# test the Element class