Model graphviz (#5118)

* Adding an example for model to graphviz

* Replacing  with

* pre commit message

* pre commit correction

Co-authored-by: Sev <[email protected]>

Author: percevalve

docs/source/api/model_graph.rst

@@ -4,3 +4,6 @@ Graphing Models
 .. currentmodule:: pymc.model_graph
 .. automodule:: pymc.model_graph
    :members:
+
+.. image:: ../images/model_to_graphviz.png
+   :width: 1000px

docs/source/images/model_to_graphviz.png

@@ -233,6 +233,31 @@ def model_to_graphviz(model=None, *, formatting: str = "plain"):
         The model to plot. Not required when called from inside a modelcontext.
     formatting : str
         one of { "plain" }
+
+    Examples
+    --------
+    How to plot the graph of the model.
+
+    .. code-block:: python
+
+        import numpy as np
+        from pymc import HalfCauchy, Model, Normal, model_to_graphviz
+
+        J = 8
+        y = np.array([28, 8, -3, 7, -1, 1, 18, 12])
+        sigma = np.array([15, 10, 16, 11, 9, 11, 10, 18])
+
+        with Model() as schools:
+
+            eta = Normal("eta", 0, 1, shape=J)
+            mu = Normal("mu", 0, sigma=1e6)
+            tau = HalfCauchy("tau", 25)
+
+            theta = mu + tau * eta
+
+            obs = Normal("obs", theta, sigma=sigma, observed=y)
+
+        model_to_graphviz(schools)
     """
     if not "plain" in formatting:
         raise ValueError(f"Unsupported formatting for graph nodes: '{formatting}'. See docstring.")