new_contents: class intSet(object):
      """
      An intSet is a set of integers
      The value is represented by a list of ints, self.vals.
      Each int in the set occurs in self.vals exactly once.
      """
      def __init__(self):
          """ Create an empty set of integers """
          self.vals = []
          
      def insert(self, e):
          """ Assumes e is an integer and inserts e into self """
          if not e in self.vals:
              self.vals.append(e)
              
      def member(self, e):
          """ Assumes e is an integer. Returns True if e is in self """
          return e in self.vals
      
      def remove(self, e):
          """ Assumes e is an integer and removes e from self
          Raise ValueError if e is not in self
          """
          try:
              self.vals.remove(e)
          except:
              raise ValueError(str(e) + ' not found')
      
      def __str__(self):
          """ Returns a string representation of self """
          self.vals.sort()
          return '{' + ','.join([str(e) for e in self.vals]) + '}'
  
subject: Add intSetClass practice