Provide property for checking if the data block has labels or not.

cml/ports/source_adapters.py

+from typing import List
 from abc import abstractmethod, ABC
 
 import pandas as pd
@@ -59,6 +60,18 @@ class PandasBlock:
     def __len__(self):
         return self.__data_block.shape[0]
 
+    @property
+    def labeled(self):
+        return not self.__data_block.Z.nunique() == 1
+
+    @property
+    def columns(self):
+        return list(self.__data_block.columns)
+
+    @property
+    def n_features(self):
+        return self.__data_block.shape[1] - self._LAST_THREE_COLUMNS
+
     def as_numpy_array(self):
         return self.__data_block[
             self.__data_block.columns[