new_contents: from astropy import units as u, constants as const
  import numpy as np
  
  Particles = {
  
      "e-": {
          "name": "electron",
          "mass": const.m_e,
          "charge": -1,
          "spin": 1/2,
          "half-life": np.inf * u.s,
          "antimatter": False,
          "generation": 1,
      },
  
      "e+": {
          "name": "positron",
          "mass": const.m_e,
          "charge": 1,
          "spin": 1/2,
          "half-life": np.inf * u.s,
          "antimatter": True,
          "generation": 1,
      },
  
      "mu-": {
          "name": "muon",
          "mass": 1.883_531_594e-28 * u.kg,
          "charge": -1,
          "spin": 1/2,
          "half-life": 2.1969811e-6 * u.s,
          "antimatter": False,
          "generation": 2,
      },
  
      "mu+": {
          "name": "antimuon",
          "mass": 1.883_531_594e-28 * u.kg,
          "charge": 1,
          "spin": 1/2,
          "half-life": 2.1969811e-6 * u.s,
          "antimatter": True,
          "generation": 2,
      },
  
      "tau-": {
          "name": "tau",
          "mass": 3.167_47e-27 * u.kg,
          "charge": -1,
          "spin": 1/2,
          "half-life": 2.906e-13 * u.s,
          "antimatter": False,
          "generation": 3,
       },
  
      "tau+": {
          "name": "antitau",
          "mass": 3.167_47e-27 * u.kg,
          "charge": 1,
          "spin": 1/2,
          "half-life": 2.906e-13 * u.s,
          "antimatter": True,
          "generation": 3,
      },
  
      "nu_e": {
          "name": "electron neutrino",
          "charge": 0,
          "spin": 1/2,
          "half-life": np.inf * u.s,
          "antimatter": False,
          "generation": 1,
      },
  
      "anti_nu_e": {
          "name": "electron antineutrino",
          "charge": 0,
          "spin": 1/2,
          "half-life": np.inf * u.s,
          "antimatter": True
          "generation": 1
      },
  
      "nu_mu": {
          "name": "muon neutrino",
          "spin": 1/2,
          "half-life": np.inf * u.s,
          "antimatter": False,
          "generation": 2,
      },
  
      "anti_nu_mu": {
          "name": "muon antineutrino",
          "spin": 1/2,
          "half-life": np.inf * u.s,
          "antimatter": True,
          "generation": 2,
      },
  
      "nu_tau": {
          "name": "tau neutrino",
          "spin": 1/2,
          "half-life": np.inf * u.s,
          "antimatter": False,
          "generation": 3,
      },
  
      "anti_nu_tau": {
          "name": "tau antineutrino",
          "spin": 1/2,
          "half-life": np.inf * u.s,
          "antimatter": True,
          "generation": 3,
      },
  
  }
  
subject: Add leptons & antileptons to new particles dict