code: def symbol(self, symbol_str, country_code=None):
          
          # If the user has not set the symbol lookup date,
          # use the end_session as the date for symbol->sid resolution.
          _lookup_date = self._symbol_lookup_date \
              if self._symbol_lookup_date is not None \
              else self.sim_params.end_session
  
          return self.asset_finder.lookup_symbol(
              symbol_str,
              as_of_date=_lookup_date,
              country_code=country_code,
          )
docs: Lookup an Equity by its ticker symbol.
  
          Parameters
          ----------
          symbol_str : str
              The ticker symbol for the equity to lookup.
          country_code : str or None, optional
              A country to limit symbol searches to.
  
          Returns
          -------
          equity : Equity
              The equity that held the ticker symbol on the current
              symbol lookup date.
  
          Raises
          ------
          SymbolNotFound
              Raised when the symbols was not held on the current lookup date.
  
          See Also
          --------
          :func:`zipline.api.set_symbol_lookup_date`