Implementing clip

[Seun-Ajayi]

Proposed changes

Implementing clip. See CLIPTextTransformer, line 449 and 455 both require _create_4d_causal_attention_mask and _prepare_4d_attention_mask respectively . You can find the implementation of this functions and the class the depend on here on transformers - https://github.com/huggingface/transformers/blob/main/src/transformers/modeling_attn_mask_utils.py

Types of changes

What types of changes does your code introduce?
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• New Model Architecture
• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)