Update of LabelTensor class and fix Simplex domain (#362)

*Implement new methods in LabelTensor and fix operators

pina/domain/difference_domain.py

@@ -77,7 +77,7 @@ class Difference(OperationInterface):
                 5
 
         """
-        if mode != self.sample_modes:
+        if mode not in self.sample_modes:
             raise NotImplementedError(
                 f"{mode} is not a valid mode for sampling."
             )

pina/domain/exclusion_domain.py

@@ -76,7 +76,7 @@ class Exclusion(OperationInterface):
                 5
 
         """
-        if mode != self.sample_modes:
+        if mode not in self.sample_modes:
             raise NotImplementedError(
                 f"{mode} is not a valid mode for sampling."
             )

pina/domain/intersection_domain.py

@@ -78,7 +78,7 @@ class Intersection(OperationInterface):
                 5
 
         """
-        if mode != self.sample_modes:
+        if mode not in self.sample_modes:
             raise NotImplementedError(
                 f"{mode} is not a valid mode for sampling."
             )

pina/domain/simplex.py

@@ -92,13 +92,12 @@ class SimplexDomain(DomainInterface):
         """
 
         span_dict = {}
-
         for i, coord in enumerate(self.variables):
-            sorted_vertices = sorted(vertices, key=lambda vertex: vertex[i])
+            sorted_vertices = torch.sort(vertices[coord].tensor.squeeze())
             # respective coord bounded by the lowest and highest values
             span_dict[coord] = [
-                float(sorted_vertices[0][i]),
-                float(sorted_vertices[-1][i]),
+                float(sorted_vertices.values[0]),
+                float(sorted_vertices.values[-1]),
             ]
 
         return CartesianDomain(span_dict)

pina/domain/union_domain.py

@@ -41,7 +41,10 @@ class Union(OperationInterface):
     
     @property
     def variables(self):
-        return list(set([geom.variables for geom in self.geometries]))
+        variables = []
+        for geom in self.geometries:
+            variables+=geom.variables
+        return list(set(variables))
 
     def is_inside(self, point, check_border=False):
         """