diff --git a/pina/label_tensor.py b/pina/label_tensor.py
index 3669272..7646dd8 100644
--- a/pina/label_tensor.py
+++ b/pina/label_tensor.py
@@ -35,14 +35,15 @@ class LabelTensor(torch.Tensor):
                     {1: {"name": "space"['a', 'b', 'c'])
 
         """
-        from .utils import check_consistency
+        self.labels = None
         if isinstance(labels, dict):
-            # check_consistency(labels, dict)
             self.update_labels(labels)
         elif isinstance(labels, list):
             self.init_labels_from_list(labels)
         elif isinstance(labels, str):
             labels = [labels]
+            self.init_labels_from_list(labels)
+        else:
             raise ValueError(f"labels must be list, dict or string.")
 
     def extract(self, label_to_extract):
@@ -184,13 +185,13 @@ class LabelTensor(torch.Tensor):
         return out
 
     def update_labels(self, labels):
-        '''
+        """
         Update the internal label representation according to the values passed as input.
 
         :param labels: The label(s) to update.
         :type labels: dict
         :raises ValueError: dof list contain duplicates or number of dof does not match with tensor shape
-        '''
+        """
         self.labels = {
             idx_: {
                 'dof': range(self.tensor.shape[idx_]),
@@ -206,11 +207,11 @@ class LabelTensor(torch.Tensor):
         self.labels.update(labels)
 
     def init_labels_from_list(self, labels):
-        '''
+        """
         Given a list of dof, this method update the internal label representation
 
         :param labels: The label(s) to update.
         :type labels: list
-        '''
+        """
         last_dim_labels = {self.tensor.ndim - 1: {'dof': labels, 'name': self.tensor.ndim - 1}}
         self.update_labels(last_dim_labels)
\ No newline at end of file