input: def validate_brackets_sequence(brackets: str):
      """ brackets is a string composed of "<" and ">" characters.
      Return True if each opening bracket has a matching closing bracket.
  
      >>> validate_brackets_sequence("<")
      False
      >>> validate_brackets_sequence("<>")
      True
      >>> validate_brackets_sequence("<<><>>")
      True
      >>> validate_brackets_sequence("><<>")
      False
      """
output:     stack = []
      for bracket in brackets:
          if bracket == '<':
              stack.append(bracket)
          elif bracket == '>':
              if not stack:
                  return False
              stack.pop()
      return not stack