code: def face_adjacency_radius(self):
          
          radii, span = graph.face_adjacency_radius(mesh=self)
          self._cache['face_adjacency_span'] = span
          return radii
docs: The approximate radius of a cylinder that fits inside adjacent faces.
  
          Returns
          ------------
          radii : (len(self.face_adjacency),) float
            Approximate radius formed by triangle pair