Deletes a Symbol.
        
        Parameters
        ----------
        symbol : str or Symbol

def delete(self, symbol):
        """
        Deletes a Symbol.
        
        Parameters
        ----------
        symbol : str or Symbol
        """
        if isinstance(symbol, (str, unicode)):
            sym = self.get(symbol)
        elif isinstance(symbol, Symbol):
            sym = symbol
        else:
            raise Exception("Invalid symbol {}".format((repr(symbol))))

        # Has to handle the case where the table would exist already
        # and where it wouldn't.
        try:
            sym.datatable = Table(sym.name, Base.metadata, autoload=True)
            sym.datatable.drop(self.eng, checkfirst=True)
        except NoSuchTableError:
            print "No worries, {} never existed to begin with.".format(sym.name)

        self.ses.delete(sym)
        self.ses.commit()