docs: def symmetrize_nonred(C):
      """Symmetrize the Wilson coefficient arrays.
  
      This function takes into account the symmetry factors
      that occur when transitioning from a basis with only non-redundant operators
      (like in WCxf) to a basis where the Wilson coefficients are symmetrized
      like the operators."""
      C_symm = {}
      for i, v in C.items():
          if i in C_symm_keys[0]:
              C_symm[i] = v.real
          elif i in C_symm_keys[1] + C_symm_keys[3]:
              C_symm[i] = v # nothing to do
          elif i in C_symm_keys[2]:
              C_symm[i] = symmetrize_2(C[i])
          elif i in C_symm_keys[4]:
              C_symm[i] = symmetrize_4(C[i])
              C_symm[i] = C_symm[i] / _d_4
          elif i in C_symm_keys[5]:
              C_symm[i] = symmetrize_5(C[i])
          elif i in C_symm_keys[6]:
              C_symm[i] = symmetrize_6(C[i])
              C_symm[i] = C_symm[i] / _d_6
          elif i in C_symm_keys[7]:
              C_symm[i] = symmetrize_7(C[i])
              C_symm[i] = C_symm[i] / _d_7
          elif i in C_symm_keys[8]:
              C_symm[i] = scale_8(C[i])
              C_symm[i] = symmetrize_8(C_symm[i])
          elif i in C_symm_keys[9]:
              C_symm[i] = symmetrize_9(C[i])
      return C_symm