docs: def write_metadata(self, symbol, metadata):
          '''
          writes user defined metadata for the given symbol
  
          Parameters
          ----------
          symbol: str
              symbol for the given item in the DB
          metadata: ?
              metadata to write
          '''
          sym = self._get_symbol_info(symbol)
          if not sym:
              raise NoDataFoundException("Symbol does not exist.")
  
          sym[USERMETA] = metadata
          self._symbols.replace_one({SYMBOL: symbol}, sym)