def __init__(self, default=None, **engines):
if default is not None:<EOL><INDENT>engines['<STR_LIT:default>'] = default<EOL><DEDENT>self.engines = engines<EOL>self.uses = set()<EOL>self.needs = set()<EOL>self.provides = set(self._provides)<EOL>for name, engine in engines.items():<EOL><INDENT>if not getattr(engine, '<STR_LIT>', None):<EOL><INDENT>engine.alias = name  <EOL><DEDENT>self.uses.update(getattr(engine, '<STR_LIT>', ()))<EOL>self.needs.update(getattr(engine, '<STR_LIT>', ()))<EOL>self.provides.update(getattr(engine, '<STR_LIT>', ()))<EOL><DEDENT>super(DatabaseExtension, self).__init__()<EOL>
Configure the database management extension.