<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def delete_node(self, key_chain):
 """ key_chain is an array of keys giving the path to the node that should be deleted. """

        node = self._data
        for key in key_chain[:-1]:
            node = node[key]

        del node[key_chain[-1]]