diff --git a/pina/__init__.py b/pina/__init__.py
index e9ce706..e69db88 100644
--- a/pina/__init__.py
+++ b/pina/__init__.py
@@ -1,6 +1,7 @@
 __all__ = [
     "Trainer", "LabelTensor", "Plotter", "Condition",
     "PinaDataModule", 'TorchOptimizer', 'Graph',
+    "RadiusGraph", "KNNGraph"
 ]
 
 from .meta import *
@@ -14,4 +15,4 @@ from .data import PinaDataModule
 
 from .optim import TorchOptimizer
 from .optim import TorchScheduler
-from .graph import Graph
+from .graph import Graph, RadiusGraph, KNNGraph
diff --git a/pina/graph.py b/pina/graph.py
index 8c16741..959bd9c 100644
--- a/pina/graph.py
+++ b/pina/graph.py
@@ -223,8 +223,8 @@ class Graph:
             return [edge_attr] * data_len
 
         if build_edge_attr:
-            return [self._build_edge_attr(x, pos_, edge_index_) for
-                    pos_, edge_index_ in zip(pos, edge_index)]
+            return [self._build_edge_attr(x_, pos_, edge_index_) for
+                    x_, pos_, edge_index_ in zip(x, pos, edge_index)]
 
 
 class RadiusGraph(Graph):