src/transformers/models/visual_bert/modeling_visual_bert.py/VisualBertEncoder/__init__
class VisualBertEncoder:    def __init__(self, config):
        super().__init__()
        self.config = config
        self.layer = nn.ModuleList([VisualBertLayer(config) for _ in range(config.num_hidden_layers)])
        self.gradient_checkpointing = False