Question: Procedure that removes repeating elements

write a procedure to remove all repeating elements from a given list
input: a list with repeating elements, such as [1, 5, 4, 1, 2, 4, 5, 1, 6]
output: a list without repeating elements
note: use list as your only structual datatype, can't convert it to set
hint:  you may use maple function has, no srting needed.
can someone help me on how to write this ? thank you
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