code: def from_coordinates(cls, coordinates, labels):
          
          from molmod.ext import molecules_distance_matrix
          distance_matrix = molecules_distance_matrix(coordinates)
          return cls(distance_matrix, labels)
docs: Initialize a similarity descriptor
  
             Arguments:
               coordinates  --  a Nx3 numpy array
               labels  --  a list with integer labels used to identify atoms of
                           the same type