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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 login_url(self, org=None):
 """ Returns the login url which will automatically log into the target Salesforce org. By default, the org_name passed to the library constructor is used but this can be overridden with the org option to log into a different org. """

        if org is None:
            org = self.org
        else:
            org = self.keychain.get_org(org)
        return org.start_url