input: def validate_bracketing(sequence: str):
      """ sequence is a string of "<" and ">".
      return True if every "<" has a matching closing ">".
  
      >>> validate_bracketing("<")
      False
      >>> validate_bracketing("<>")
      True
      >>> validate_bracketing("<<><>>")
      True
      >>> validate_bracketing("><<>")
      False
      """
output:     stack = []
      for char in sequence:
          if char == "<":
              stack.append(char)
          elif char == ">":
              if not stack:
                  return False
              stack.pop()
      return len(stack) == 0