ApproximateGELU  
The approximate form of the Gaussian Error Linear Unit (GELU). For more details, see section 2 of this
[paper](https://arxiv.org/abs/1606.08415).  
Parameters:
dim_in (`int`): The number of channels in the input.
dim_out (`int`): The number of channels in the output.
bias (`bool`, defaults to True): Whether to use a bias in the linear layer.