@property<EOL><INDENT>def flux_expression(self):<DEDENT>
if self.model is not None:<EOL><INDENT>return <NUM_LIT:1.> * self.forward_variable - <NUM_LIT:1.> * self.reverse_variable<EOL><DEDENT>else:<EOL><INDENT>return None<EOL><DEDENT>
Forward flux expression

        Returns
        -------
        sympy expression
            The expression representing the the forward flux (if associated
            with model), otherwise None. Representing the net flux if
            model.reversible_encoding == 'unsplit' or None if reaction is
            not associated with a model