input: Write a python function to remove an element from a list if it exists.
  assert remove_element(['abc', '123', '345'], '123') == ['abc', '345']
  assert remove_element(['abc', '123', '345'], '678') == ['abc', '123', '345']
  assert remove_element(['abc', '123', '345', '123'], '123') == ['abc', '345', '123']
output: def remove_element(lst, element):
      if element in lst:
          lst.remove(element)
      return lst