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Solve the following problem using Python, implementing the functions described below, one line at a time
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<USER_TASK:>
Description:
 def add_user_role(self, user_role):
 """ Add the specified User Role to this User. This User must not be a system-defined or pattern-based user. Authorization requirements: * Task permission to the "Manage Users" task to modify a standard user or the "Manage User Templates" task to modify a template user. Parameters: user_role (:class:`~zhmcclient.UserRole`):
 User Role to be added. Must not be `None`. Raises: :exc:`~zhmcclient.HTTPError` :exc:`~zhmcclient.ParseError` :exc:`~zhmcclient.AuthError` :exc:`~zhmcclient.ConnectionError` """

        body = {
            'user-role-uri': user_role.uri
        }
        self.manager.session.post(
            self.uri + '/operations/add-user-role',
            body=body)