from torch import nn


def get_activation(act_fn: str) -> nn.Module:
    """Helper function to get activation function from string.

    Args:
        act_fn (str): Name of activation function.

    Returns:
        nn.Module: Activation function.
    """
    if act_fn in ["swish", "silu"]:
        return nn.SiLU()
    elif act_fn == "mish":
        return nn.Mish()
    elif act_fn == "gelu":
        return nn.GELU()
    elif act_fn == "relu":
        return nn.ReLU()
    else:
        raise ValueError(f"Unsupported activation function: {act_fn}")