code: def get_rotatable_bonds(self,mol):
  		
  		RotatableBondSmarts = Chem.MolFromSmarts('[!$(*#*)&!D1]-&!@[!$(*#*)&!D1]')
  		bonds = mol.GetSubstructMatches(RotatableBondSmarts,uniquify=1)
  		return bonds
docs: Determines rotatable bonds in a ligand molecule
  		Takes:
  			* mol * - mol file in rdkit environment
  		Output:
  			* bonds * - tuples of atom ids