'Reduces the atom to an affine expression and list of constraints.
Parameters
arg_objs : list
LinExpr for each argument.
size : tuple
The size of the resulting expression.
data :
Additional data required by the atom.
Returns
tuple
(LinOp for objective, list of constraints)'

@staticmethod
def graph_implementation(arg_objs, size, data=None):

    x = arg_objs[0]
    t = lu.create_var(x.size)
    constraints = [lu.create_geq(lu.sum_expr([x, t])), lu.create_leq(x, t)]
    return (t, constraints)
