Unbind the instance
        
        Args:
            binding (AtlasServiceBinding.Binding): Existing or New binding

def unbind(self, binding):
        """ Unbind the instance
        
        Args:
            binding (AtlasServiceBinding.Binding): Existing or New binding
        """
        
        username = self.backend.config.generate_binding_username(binding)
        
        try:
            self.backend.atlas.DatabaseUsers.delete_a_database_user(username)
        except ErrAtlasNotFound:
            # The user does not exist. This is not an issue because this is possible that we
            # removed it in a previous call that failed later on the broker.
            # This cover a manually deleted user case too.
            pass

        self.backend.storage.remove(binding)