| 
  | _findDativeSite(self,
        site)
   |  |  Normally, we'd put the X-Metal bond on the same vector as the X-Y bond
  vector, where Y is the atom that is being removed.  However, for a dative
  X-Metal bond, there is no atom to remove and therefore, there is no 
  predefined bond vector for the X-Metal bond.  Find the best vector and 
  place an atom there for removal later. 
    Parameters:
        site(tuple) - (X, Y) tuple indicating the index of atom X, which will be bonded
          to the metal atom.  Y is ignored.Returns: tuple(X, Y) tuple, where Y is a new atom added on the vector that the 
          X-Metal bond should be made. |