Implement functions related to the double$-$chained list. These functions should be included in the class.

$$ Remove from a list of doubles all the elements that are present multiple times: we consider the list to be unsorted.

$$ Remove from a list of doubles all the elements that are present multiple times: we consider the list to be sorted.

$$ Create a function that returns, from a list of doubles, a list that contains $2$ elements in each node: the value of an element from the list given as an input, and the number of times this element is present in the list given as an output.

For each method of the class Double Chained List, provide an example illustrating how the function can be used. In c$++$