code: def posterior(self, x):
          
          if self._post is None:
              return self._posterior(x)
          x = np.array(x, ndmin=1)
          return self._post_interp(x)
docs: Posterior function.
  
           Returns ``P(x) = \int L(x,y|z') L(y) dy / \int L(x,y|z') L(y) dx dy``
  
          This will used the cached '~fermipy.castro.Interpolator' 
          object if possible, and construct it if needed.