Make parent class signature match child classes (#3207)

* Make parent class signature match child classes

* Write down docs

Author: ColCarroll

pymc3/step_methods/hmc/quadpotential.py

@@ -94,8 +94,23 @@ def update(self, sample, grad, tune):
         """
         pass
 
-    def raise_ok(self):
-        pass
+    def raise_ok(self, vmap=None):
+        """Check if the mass matrix is ok, and raise ValueError if not.
+
+        Parameters
+        ----------
+        vmap : blocking.ArrayOrdering.vmap
+            List of `VarMap`s, which are namedtuples with var, slc, shp, dtyp
+
+        Raises
+        ------
+        ValueError if any standard deviations are 0 or infinite
+
+        Returns
+        -------
+        None
+        """
+        return None
 
     def reset(self):
         pass
@@ -186,6 +201,21 @@ def update(self, sample, grad, tune):
         self._n_samples += 1
 
     def raise_ok(self, vmap):
+        """Check if the mass matrix is ok, and raise ValueError if not.
+
+        Parameters
+        ----------
+        vmap : blocking.ArrayOrdering.vmap
+            List of `VarMap`s, which are namedtuples with var, slc, shp, dtyp
+
+        Raises
+        ------
+        ValueError if any standard deviations are 0 or infinite
+
+        Returns
+        -------
+        None
+        """
         if np.any(self._stds == 0):
             name_slc = []
             tmp_hold = list(range(self._stds.size))