docs: def wcxf2arrays(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. This is needed for the parsing
      of input in WCxf format."""
      C = {}
      for k, v in d.items():
          name = k.split('_')[0]
          s = C_keys_shape[name]
          if s == 1:
              C[k] = v
          else:
              ind = k.split('_')[-1]
              if name not in C:
                  C[name] = np.zeros(s, dtype=complex)
              C[name][tuple([int(i) - 1 for i in ind])] = v
      return C