Keyword to describe the chmical reactions

Parameters:

reactions (type: list of Reaction) list of reactions
[modele_micro_melange] (type: int) modele_micro_melange (0 by default)
[constante_modele_micro_melange] (type: float) constante of modele (1 by default)
[espece_en_competition_micro_melange] (type: string) espece in competition in reactions