如何在pyomo中构造分段步长函数

from pyomo.environ import *

# 创建一个模型对象
model = ConcreteModel()

# 定义变量
model.x = Var(within=NonNegativeReals)

# 定义分段步长函数的参数
breakpoints = [0, 1, 2, 3]  # 分段点
slopes = [1, 2, 3, 4]  # 斜率

# 定义约束条件
def piecewise_rule(model):
    expr = 0
    for i in range(len(breakpoints)-1):
        expr += slopes[i] * (model.x - breakpoints[i])
        expr.setlb(0)  # 设置下界为0，确保函数是非负的
    return expr

model.piecewise_constraint = Constraint(rule=piecewise_rule)

# 定义目标函数
model.obj = Objective(expr=model.x)

# 求解模型
solver = SolverFactory('glpk')
solver.solve(model)

# 输出结果
print("x =", model.x())