code: def get_covalent_bonds(self, tol=0.2):
          
          bonds = []
          for site1, site2 in itertools.combinations(self._sites, 2):
              if CovalentBond.is_bonded(site1, site2, tol):
                  bonds.append(CovalentBond(site1, site2))
          return bonds
docs: Determines the covalent bonds in a molecule.
  
          Args:
              tol (float): The tol to determine bonds in a structure. See
                  CovalentBond.is_bonded.
  
          Returns:
              List of bonds