ditioning with class_embed_type equal to None.
time_embedding_type (str, optional, defaults to positional):
The type of position embedding to use for timesteps. Choose from positional or fourier.
time_embedding_dim (int, optional, defaults to None):
An optional override for the dimension of the projected time embedding.
time_embedding_act_fn (str, optional, defaults to None):
Optional activation function to use only once on the time embeddings 