code: def _read_fasta(fasta_file, output_dict):
      
      read_name = None
      with open(fasta_file, 'r') as f:
          for line in f:
              line = line.strip()
              if not line:
                  continue
              if line.startswith('>'):
                  read_name = line.lstrip('>')
              else:
                  assert read_name is not None, line
                  output_dict[read_name].append(line.strip())
      return output_dict
docs: Read the peptide fasta into an existing dict.
  
      :param str fasta_file: The peptide file
      :param dict output_dict: The dict to appends results to.
      :return: output_dict
      :rtype: dict