docs: def _read_fam(self):
          """Reads the FAM file."""
          # Reading the FAM file and setting the values
          fam = pd.read_csv(self.fam_filename, delim_whitespace=True,
                            names=["fid", "iid", "father", "mother", "gender",
                                   "status"],
                            dtype=dict(fid=str, iid=str, father=str, mother=str))
  
          # Getting the byte and bit location of each samples
          fam["byte"] = [
              int(np.ceil((1 + 1) / 4.0)) - 1 for i in range(len(fam))
          ]
          fam["bit"] = [(i % 4) * 2 for i in range(len(fam))]
  
          # Saving the data in the object
          self._fam = fam
          self._nb_samples = self._fam.shape[0]