Bring Flax attention naming in sync with PyTorch (#2511)

Bring flax attention naming in sync with PyTorch.

Author: pcuenca

src/diffusers/models/attention_flax.py

@@ -16,7 +16,7 @@
 import jax.numpy as jnp
 
 
-class FlaxAttentionBlock(nn.Module):
+class FlaxCrossAttention(nn.Module):
     r"""
     A Flax multi-head attention module as described in: https://arxiv.org/abs/1706.03762
 
@@ -118,10 +118,10 @@ class FlaxBasicTransformerBlock(nn.Module):
 
     def setup(self):
         # self attention (or cross_attention if only_cross_attention is True)
-        self.attn1 = FlaxAttentionBlock(self.dim, self.n_heads, self.d_head, self.dropout, dtype=self.dtype)
+        self.attn1 = FlaxCrossAttention(self.dim, self.n_heads, self.d_head, self.dropout, dtype=self.dtype)
         # cross attention
-        self.attn2 = FlaxAttentionBlock(self.dim, self.n_heads, self.d_head, self.dropout, dtype=self.dtype)
-        self.ff = FlaxGluFeedForward(dim=self.dim, dropout=self.dropout, dtype=self.dtype)
+        self.attn2 = FlaxCrossAttention(self.dim, self.n_heads, self.d_head, self.dropout, dtype=self.dtype)
+        self.ff = FlaxFeedForward(dim=self.dim, dropout=self.dropout, dtype=self.dtype)
         self.norm1 = nn.LayerNorm(epsilon=1e-5, dtype=self.dtype)
         self.norm2 = nn.LayerNorm(epsilon=1e-5, dtype=self.dtype)
         self.norm3 = nn.LayerNorm(epsilon=1e-5, dtype=self.dtype)
@@ -242,10 +242,14 @@ def __call__(self, hidden_states, context, deterministic=True):
         return hidden_states
 
 
-class FlaxGluFeedForward(nn.Module):
+class FlaxFeedForward(nn.Module):
     r"""
-    Flax module that encapsulates two Linear layers separated by a gated linear unit activation from:
+    Flax module that encapsulates two Linear layers separated by a non-linearity. It is the counterpart of PyTorch's
+    [`FeedForward`] class, with the following simplifications:
+    - The activation function is currently hardcoded to a gated linear unit from:
     https://arxiv.org/abs/2002.05202
+    - `dim_out` is equal to `dim`.
+    - The number of hidden dimensions is hardcoded to `dim * 4` in [`FlaxGELU`].
 
     Parameters:
         dim (:obj:`int`):