pub trait Problem {
// Required methods
fn add_objective_expression(&mut self, expr_arena: &mut LpExpression);
fn add_constraints(&mut self, contraint_expr: &LpConstraint);
}pub trait Problem {
// Required methods
fn add_objective_expression(&mut self, expr_arena: &mut LpExpression);
fn add_constraints(&mut self, contraint_expr: &LpConstraint);
}