code: def get_small_molecule_refs(self, hms_lincs_id):
          
          refs = {'HMS-LINCS': hms_lincs_id}
  
          entry = self._get_entry_by_id(self._sm_data, hms_lincs_id)
          # If there is no entry for this ID
          if not entry:
              return refs
  
          # If there is an entry then fill up the refs with existing values
          mappings = dict(chembl='ChEMBL ID', chebi='ChEBI ID',
                          pubchem='PubChem CID', lincs='LINCS ID')
          for k, v in mappings.items():
              if entry.get(v):
                  refs[k.upper()] = entry.get(v)
          return refs
docs: Get the id refs of a small molecule from the LINCS sm metadata.
  
          Parameters
          ----------
          hms_lincs_id : str
              The HMS LINCS ID of the small molecule.
  
          Returns
          -------
          dict
              A dictionary of references.