code: def write_genotypes(self, genotypes):
          
          if self._mode != "w":
              raise UnsupportedOperation("not available in 'r' mode")
  
          # Initializing the number of samples if required
          if self._nb_values is None:
              self._nb_values = len(genotypes)
  
          # Checking the expected number of samples
          if self._nb_values != len(genotypes):
              raise ValueError("{:,d} samples expected, got {:,d}".format(
                  self._nb_values,
                  len(genotypes),
              ))
  
          # Writing to file
          byte_array = [
              g[0] | (g[1] << 2) | (g[2] << 4) | (g[3] << 6) for g in
              self._grouper((_byte_recode[geno] for geno in genotypes), 4)
          ]
          self._bed.write(bytearray(byte_array))
docs: Write genotypes to binary file.
  
          Args:
              genotypes (numpy.ndarray): The genotypes to write in the BED file.