@property<EOL><INDENT>def reverse_variable(self):<DEDENT>
if self.model is not None:<EOL><INDENT>return self.model.variables[self.reverse_id]<EOL><DEDENT>else:<EOL><INDENT>return None<EOL><DEDENT>
An optlang variable representing the reverse flux

        Returns
        -------
        optlang.interface.Variable
            An optlang variable for the reverse flux or None if reaction is
            not associated with a model.