code: def alignment_to_partials(alignment, missing_data=None):
      
      partials_dict = {}
      for (name, sequence) in alignment.get_sequences():
          datatype = 'dna' if alignment.is_dna() else 'protein'
          partials_dict[name] = seq_to_partials(sequence, datatype)
  
      if missing_data is not None:
          l = len(alignment)
          for name in missing_data:
              if name not in partials_dict:
                  partials_dict[name] = seq_to_partials('-'*l, datatype)
      return partials_dict
docs: Generate a partials dictionary from a treeCl.Alignment