code: def get_nearest_site(self, coords, site, r=None):
          
          index = self.index(site)
          if r is None:
              r = np.linalg.norm(np.sum(self.lattice.matrix, axis=0))
          ns = self.get_sites_in_sphere(coords, r, include_index=True)
          # Get sites with identical index to site
          ns = [n for n in ns if n[2] == index]
          # Sort by distance to coords
          ns.sort(key=lambda x: x[1])
          # Return PeriodicSite and distance of closest image
          return ns[0][0:2]
docs: Given coords and a site, find closet site to coords.
          Args:
              coords (3x1 array): cartesian coords of center of sphere
              site: site to find closest to coords
              r: radius of sphere. Defaults to diagonal of unit cell
  
          Returns:
              Closest site and distance.