code: def mesh(self,xyzs):
          
          I,J,K = self.powers
          d = np.asarray(xyzs,'d')-self.origin
          # Got help from stackoverflow user @unutbu with this.
          # See: http://stackoverflow.com/questions/17391052/compute-square-distances-from-numpy-array
          d2 = np.einsum('ij,ij -> i',d,d)
          return self.norm*d[:,0]**I*d[:,1]**J*d[:,2]**K*np.exp(-self.exponent*d2)
docs: Evaluate basis function on a mesh of points *xyz*.