I'm using Zope 2.8.8 and I trying to make my own product.

Whenever I make a product with errors in the python coding, I could see my product name registered in the product management page. But when I fix all the error, the product disappears; it not in the product management page or the add menu.

What is the problem here?

here is my coding

__init__.py--------

-------------------

import helloModule

def initialize(context):
    context.registerClass(
        helloModule.helloClass,
        permission="Add Hello Object",
        constructor=(
            helloModule.manage_addHelloForm,
            helloModule.manage_addHello
        )
    )

helloModule.py--------

------------------------

def manage_addHelloForm(self):
    " Form for adding a Hello Object "
    return """
        <html>
            <head>
                <title></title>
            </head>

            <body>
                <form method="post" action="./manage_addHello">
                    <input type=text name=id>
                    <input type=submit value="Add Hello">
                </form>
            </body>
        </html>
    """

def manage_addHello(self):
    " Method for adding a Hello Object "
    newHello=helloClass(id)
    self._setObject(id, newHello)
    return self.manage_main(self, REQUEST)

class helloClass:
    meta_type='Hello Object'

    def __init__(self, name='World'):
        self.name=name

def saySomething(self):
return "Hello, " + self.name

def edit(self, name):
self.name=name