Fix typo tutorial geometry (#259)

* is_inside -> sample rename

docs/source/_rst/tutorials/tutorial6/tutorial.rst

@@ -261,7 +261,7 @@ add in “pass” for the moment.
         def sample(self):
             pass
 
-Now we have the skeleton for our ``Heart`` class. The ``is_inside``
+Now we have the skeleton for our ``Heart`` class. The ``sample``
 method is where most of the work is done so let’s fill it out.
 
 .. code:: ipython3

tutorials/tutorial6/tutorial.ipynb

@@ -422,7 +422,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "Now we have the skeleton for our `Heart` class. The `is_inside` method is where most of the work is done so let's fill it out."
+    "Now we have the skeleton for our `Heart` class. The `sample` method is where most of the work is done so let's fill it out."
    ]
   },
   {

tutorials/tutorial6/tutorial.py

@@ -198,7 +198,7 @@ class Heart(Location):
         pass
 
 
-# Now we have the skeleton for our `Heart` class. The `is_inside` method is where most of the work is done so let's fill it out.
+# Now we have the skeleton for our `Heart` class. The `sample` method is where most of the work is done so let's fill it out.
 
 # In[14]: