docs: def retrieve_equities(self, sids):
          """
          Retrieve Equity objects for a list of sids.
  
          Users generally shouldn't need to this method (instead, they should
          prefer the more general/friendly `retrieve_assets`), but it has a
          documented interface and tests because it's used upstream.
  
          Parameters
          ----------
          sids : iterable[string]
  
          Returns
          -------
          equities : dict[str -> Equity]
  
          Raises
          ------
          EquitiesNotFound
              When any requested asset isn't found.
          """
          cache = self._asset_cache
  
          try:
              return {
                  k: cache[k]
                  for k in sids
              }
          except KeyError:
              raise EquitiesNotFound(sids=sids)