code: def make_Hs_implicit(original_mol, keep_stereo=True):
      
      mol = clone(original_mol)
      mol.descriptors.clear()  # Reset descriptor
      to_remove = set()
      for i, nbrs in mol.neighbors_iter():
          if mol.atom(i).symbol == "H":  # do not remove H2
              continue
          for nbr, bond in nbrs.items():
              if mol.atom(nbr).symbol == "H" and \
                      not (bond.order == 1 and bond.type and keep_stereo):
                  to_remove.add(nbr)
      for r in to_remove:
          mol.remove_atom(r)
      assign_descriptors(mol)
      return mol
docs: Return molecule that explicit hydrogens removed
      TODO: this query function should be renamed to "explicitHs_removed"