input: from typing import List
  
  def determine_triangle_type(sides: List[int]) -> str:
      """
      You are given a 0-indexed integer array sides of size 3 which represents the lengths of a triangle's sides.
  
      A triangle is considered equilateral if all three sides are of equal length.
      A triangle is considered isosceles if exactly two of its sides are of the same length.
      A triangle is considered scalene if all its sides are of different lengths.
      Return a string indicating the type of triangle that can be formed, or "none" if the given sides cannot form a valid triangle.
  
      Examples:
      >>> sides = [3, 3, 3]
      "equilateral"
      >>> sides = [3, 4, 5]
      "scalene"
  
      Constraints:
      sides.length == 3
      1 <= sides[i] <= 100
      """
output:     a, b, c = sorted(sides)
      if a + b <= c:
          return "none"
      if a == b == c:
          return "equilateral"
      elif a == b or b == c or a == c:
          return "isosceles"
      else:
          return "scalene"