Gets a Symbol based on name, which may or may not exist.
        
        Parameters
        ----------
        symbol : str
        
        Returns
        -------
        Symbol or None.  
        
        Note
        ----
        Use .get(), if the symbol should exist, and an exception 
        is needed if it doesn't.

def try_to_get(self, symbol):
        """ Gets a Symbol based on name, which may or may not exist.
        
        Parameters
        ----------
        symbol : str
        
        Returns
        -------
        Symbol or None.  
        
        Note
        ----
        Use .get(), if the symbol should exist, and an exception 
        is needed if it doesn't.

        """
        syms = self.ses.query(Symbol).filter(Symbol.name == symbol).all()
        if len(syms) == 0:
            return None
        else:
            return syms[0]