code: def test_solve_constraint():
      from mystic.math.measures import mean
  
      @with_mean(1.0)
      def constraint(x):
          x[-1] = x[0]
          return x
  
      x = solve(constraint, guess=[2, 3, 1])
      # x = solve(constraint, solver='buckshot')
  
      assert almostEqual(mean(x), 1.0, tol=1e-15)
      assert x[-1] == x[0]
      assert issolution(constraint, x)
  
file_path: mystic/mystic/tests/test_constraints.py
imports: from mystic.constraints import *
  from mystic.penalty import quadratic_equality
  from mystic.coupler import inner
  from mystic.math import almostEqual
  from mystic.tools import random_seed
label_desc: Use image node_id 3 for calling a global function with example usage: test_solve_constraint() and returns: x