How to perform relaxedFBA with cobrapy? about cobrapy HOT 1 CLOSED

from cobra.io import load_model
from numpy import Inf

mod = load_model("textbook")
print(mod.summary())

mod.reactions.Biomass_Ecoli_core.lower_bound = 1
print(mod.optimize())  # infeasible


def relaxed_bounds_fba(model, exclude=None):
    """Relax the bounds to achieve feasibility.

    Arguments
    ---------
    model : cobra.Model
        A cobra model with an infeasible constraint.
    exclude : list of str
        Reaction IDs which should not be relaxed.

    Returns
    -------
    A relaxed model solution.
    """
    relaxations = []
    constraints = []

    with model:
        for rxn in mod.reactions:
            if rxn.id in exclude:
                continue
            p = mod.problem.Variable(f"p_{rxn.id}", lb=0)  # lower bounds relaxation
            q = mod.problem.Variable(f"q_{rxn.id}", lb=0)  # upper bound relaxation
            const = mod.problem.Constraint(                # relaxed flux
                rxn.flux_expression + p - q,
                lb=rxn.lower_bound,
                ub=rxn.upper_bound,
                name=f"relaxed_{rxn.id}"
            )
            relaxations.extend([p, q])
            constraints.append(const)
            rxn.bounds = -Inf, Inf                         # deactivate the "old" bounds

        mod.add_cons_vars(relaxations + constraints)
        mod.objective = sum(relaxations)                   # minimize relaxation
        mod.objective_direction = "min"
        relaxed_sol = mod.optimize()
    return relaxed_sol

rs = relaxed_bounds_fba(mod, exclude=["Biomass_Ecoli_core"])
print(mod.summary(solution=rs))