code: def find_eq_stress(strains, stresses, tol=1e-10):
      
      stress_array = np.array(stresses)
      strain_array = np.array(strains)
      eq_stress = stress_array[np.all(abs(strain_array)<tol, axis=(1,2))]
  
      if eq_stress.size != 0:
          all_same = (abs(eq_stress - eq_stress[0]) < 1e-8).all()
          if len(eq_stress) > 1 and not all_same:
              raise ValueError("Multiple stresses found for equilibrium strain"
                               " state, please specify equilibrium stress or  "
                               " remove extraneous stresses.")
          eq_stress = eq_stress[0]
      else:
          warnings.warn("No eq state found, returning zero voigt stress")
          eq_stress = Stress(np.zeros((3, 3)))
      return eq_stress
docs: Finds stress corresponding to zero strain state in stress-strain list
  
      Args:
          strains (Nx3x3 array-like): array corresponding to strains
          stresses (Nx3x3 array-like): array corresponding to stresses
          tol (float): tolerance to find zero strain state