def get_exchange_reactions(model):
    """Yield IDs of all exchange reactions from model.

    This helper function would be useful when creating
    :class:`.ReactionDeletionStrategy` objects.

    Args:
        model: :class:`psamm.metabolicmodel.MetabolicModel`.
    """
    for reaction_id in model.reactions:
        if model.is_exchange(reaction_id):
            yield reaction_id
