diff --git a/jedi/api/classes.py b/jedi/api/classes.py
index c5767933..2563f8f7 100644
--- a/jedi/api/classes.py
+++ b/jedi/api/classes.py
@@ -357,6 +357,16 @@ class BaseDefinition(object):
 
         return self._name.get_root_context().is_stub()
 
+    def is_side_effect(self):
+        """
+        Checks if a name is defined as ``self.foo = 3``. In case of self, this
+        function would return False, for foo it would return True.
+        """
+        tree_name = self._name.tree_name
+        if tree_name is None:
+            return False
+        return tree_name.is_definition() and tree_name.parent.type == 'trailer'
+
     def goto(self, **kwargs):
         with debug.increase_indent_cm('goto for %s' % self._name):
             return self._goto(**kwargs)
@@ -703,16 +713,6 @@ class Definition(BaseDefinition):
         else:
             return self._name.tree_name.is_definition()
 
-    def is_side_effect(self):
-        """
-        Checks if a name is defined as ``self.foo = 3``. In case of self, this
-        function would return False, for foo it would return True.
-        """
-        tree_name = self._name.tree_name
-        if tree_name is None:
-            return False
-        return tree_name.is_definition() and tree_name.parent.type == 'trailer'
-
     def __eq__(self, other):
         return self._name.start_pos == other._name.start_pos \
             and self.module_path == other.module_path \