.. _pytorch-ops-torch.nn.transformer-encoder:

modelzoo.common.pytorch.layers.TransformerEncoder
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import path: ``modelzoo.common.pytorch.layers.TransformerEncoder``

**TransformerEncoder** (encoder_layer, num_layers, norm=None, enable_nested_tensor=False):

- **encoder_layer**: an instance of the TransformerEncoderLayer() class (required). 

- **num_layers**: the number of sub-encoder-layers in the encoder (required). 

- **norm**: the layer normalization component (optional). 

**forward** (src, mask=None, src_key_padding_mask=None):

- **src** (Tensor): the sequence to the encoder (required). shape ``[batch_size, src_seq_length, embed_dim]``.

- **mask** (Tensor): the mask for the src sequence (optional). shape ``[src_seq_length, src_seq_length]``.

- **src_key_padding_mask (Tensor)**: the mask for the src keys per batch (optional). shape ``[batch_size, src_seq_length]``.