docs: def wcxf2arrays_symmetrized(d):
      """Convert a dictionary with a Wilson coefficient
      name followed by underscore and numeric indices as keys and numbers as
      values to a dictionary with Wilson coefficient names as keys and
      numbers or numpy arrays as values.
  
  
      In contrast to `wcxf2arrays`, here the numpy arrays fulfill the same
      symmetry relations as the operators (i.e. they contain redundant entries)
      and they do not contain undefined indices.
  
      Zero arrays are added for missing coefficients."""
      C = wcxf2arrays(d)
      C = symmetrize_nonred(C)
      C = add_missing(C)
      return C