def find_biomass_reaction(
    model, biomass_string=["Biomass", "BIOMASS", "biomass"]
):
    """
    Identifies the biomass reaction(s) in a metabolic model.

    Parameters
    ----------
    model : cobra.Model
        Metabolic model.
    biomass_string : str or list
        String denoting at least a part of the name of the
        biomass function of the metabolic model or a list
        containing multiple possibilities to be tested.
        Preset to `["Biomass", "BIOMASS", "biomass"]`.

    Returns
    -------
    biomass_reaction_ids : list
        Reaction(s) containing the input string.
    """
    if isinstance(biomass_string, list):
        biomass = biomass_string
    else:
        biomass = list(biomass_string)
    biomass_reaction_ids = []
    for reaction in model.reactions:
        for biomass_spelling in biomass:
            if biomass_spelling in reaction.id:
                biomass_reaction_ids.append(reaction.id)
    return biomass_reaction_ids