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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def oauth_signup(self, provider, attrs, defaults, redirect_url=None):
 """Start the signup process after having logged in via oauth """

        session["oauth_user_defaults"] = defaults
        session["oauth_user_attrs"] = dict(provider=provider, **attrs)
        if not redirect_url:
            redirect_url = request.args.get("next")
        return redirect(url_for('users.oauth_signup', next=redirect_url))