def METHOD_NAME(self, node):
    """Boolean operator handler."""
    op = self.op_mapper[node.op.__class__]
    self.ops.append([])
    for value in node.values:
        self.visit(value)
    c = self.ops.pop()
    if self.ops:
        self.ops[-1].append({op: c})
    else:
        self.mongo_query[op] = c