def __add__(self, other):
new_reaction = self.copy()<EOL>if other == <NUM_LIT:0>:<EOL><INDENT>return new_reaction<EOL><DEDENT>else:<EOL><INDENT>new_reaction += other<EOL><DEDENT>return new_reaction<EOL>
Add two reactions

        The stoichiometry will be the combined stoichiometry of the two
        reactions, and the gene reaction rule will be both rules combined by an
        and. All other attributes (i.e. reaction bounds) will match those of
        the first reaction