docs: def find_previous(element, l):
      """
      find previous element in a sorted list
  
      >>> find_previous(0, [0])
      0
      >>> find_previous(2, [1, 1, 3])
      1
      >>> find_previous(0, [1, 2])
      >>> find_previous(1.5, [1, 2])
      1
      >>> find_previous(3, [1, 2])
      2
      """
      length = len(l)
      for index, current in enumerate(l):
          # current is the last element
          if length - 1 == index:
              return current
  
          # current is the first element
          if index == 0:
              if element < current:
                  return None
  
          if current <= element < l[index+1]:
              return current