add an assert for relative positional keyword arguments

setup.py

@@ -3,7 +3,7 @@
 setup(
   name = 'x-transformers',
   packages = find_packages(exclude=['examples']),
-  version = '0.8.1',
+  version = '0.8.2',
   license='MIT',
   description = 'X-Transformers - Pytorch',
   author = 'Phil Wang',

x_transformers/x_transformers.py

@@ -404,6 +404,8 @@ def __init__(
 
         self.has_pos_emb = position_infused_attn or rel_pos_bias
         self.pia_pos_emb = FixedPositionalEmbedding(dim) if position_infused_attn else None
+
+        assert rel_pos_num_buckets < rel_pos_max_distance, 'number of relative position buckets must be less than the relative position max distance'
         self.rel_pos = RelativePositionBias(causal = causal, heads = heads, num_buckets = rel_pos_num_buckets, max_distance = rel_pos_max_distance) if rel_pos_bias else None
 
         self.pre_norm = pre_norm and not residual_attn