docs: def get_cod_ids(self, formula):
          """
          Queries the COD for all cod ids associated with a formula. Requires
          mysql executable to be in the path.
  
          Args:
              formula (str): Formula.
  
          Returns:
              List of cod ids.
          """
          # TODO: Remove dependency on external mysql call. MySQL-python package does not support Py3!
  
          # Standardize formula to the version used by COD.
  
          sql = 'select file from data where formula="- %s -"' % \
              Composition(formula).hill_formula
          text = self.query(sql).split("\n")
          cod_ids = []
          for l in text:
              m = re.search(r"(\d+)", l)
              if m:
                  cod_ids.append(int(m.group(1)))
          return cod_ids