Feature request: GroupedNaturalConversion

[djinnome]

Hi folks,

We really like MIRA and would love to use it on metabolic networks specified in SBML, but we noticed that a current limitation of the mira metamodel is that NaturalConversion only specifies a single reactant and a single product.

Could we specify a new GroupedNaturalConversion class that takes multiple reactants and multiple products?

for example,

$$\text{A}+ \text{B} \rightarrow \text{C} + \text{D}$$