docs: def define_frequencies(Ne, explicitly_antisymmetric=False):
      u"""Define all frequencies omega_level, omega, gamma.
  
      >>> from sympy import pprint
      >>> pprint(define_frequencies(2), use_unicode=True)
      ⎛          ⎡ 0   ω₁₂⎤  ⎡ 0   γ₁₂⎤⎞
      ⎜[ω₁, ω₂], ⎢        ⎥, ⎢        ⎥⎟
      ⎝          ⎣ω₂₁   0 ⎦  ⎣γ₂₁   0 ⎦⎠
  
      We can make these matrices explicitly antisymmetric.
  
      >>> pprint(define_frequencies(2, explicitly_antisymmetric=True),
      ...                           use_unicode=True)
      ⎛          ⎡ 0   -ω₂₁⎤  ⎡ 0   -γ₂₁⎤⎞
      ⎜[ω₁, ω₂], ⎢         ⎥, ⎢         ⎥⎟
      ⎝          ⎣ω₂₁   0  ⎦  ⎣γ₂₁   0  ⎦⎠
  
      """
      omega_level = [Symbol('omega_'+str(i+1), real=True) for i in range(Ne)]
  
      if Ne > 9:
          opening = "\\"
          comma = ","
          open_brace = "{"
          close_brace = "}"
      else:
          opening = r""
          comma = ""
          open_brace = ""
          close_brace = ""
  
      omega = []; gamma = []
      for i in range(Ne):
          row_omega = []; row_gamma = []
          for j in range(Ne):
              if i == j:
                  om = 0; ga = 0
              elif i > j:
                  om = Symbol(opening+r"omega_" +
                              open_brace+str(i+1)+comma+str(j+1) +
                              close_brace, real=True)
                  ga = Symbol(opening+r"gamma_" +
                              open_brace+str(i+1)+comma+str(j+1) +
                              close_brace, real=True)
              elif explicitly_antisymmetric:
                  om = -Symbol(opening+r"omega_" +
                               open_brace+str(j+1)+comma+str(i+1) +
                               close_brace, real=True)
                  ga = -Symbol(opening+r"gamma_" +
                               open_brace+str(j+1)+comma+str(i+1) +
                               close_brace, real=True)
              else:
                  om = Symbol(opening+r"omega_" +
                              open_brace+str(i+1)+comma+str(j+1) +
                              close_brace, real=True)
                  ga = Symbol(opening+r"gamma_" +
                              open_brace+str(i+1)+comma+str(j+1) +
                              close_brace, real=True)
  
              row_omega += [om]
              row_gamma += [ga]
  
          omega += [row_omega]
          gamma += [row_gamma]
  
      omega = Matrix(omega)
      gamma = Matrix(gamma)
  
      return omega_level, omega, gamma