projected `hidden_states`. The actual length of the used `hidden_states` is `num_embeddings +
additional_embeddings`.
dropout (`float`, *optional*, defaults to 0.0): The dropout probability to use.
time_embed_act_fn (`str`, *optional*, defaults to 'silu'):
The activation function to use to create timestep embeddings.
norm_in_type (`str`, *optional*, defaults to None): The normalization layer to apply on hidden states before
passing to Transformer blocks. Set it to `None` if normalization is not needed.