code: def merge_to_one_seq(infile, outfile, seqname='union'):
      '''Takes a multi fasta or fastq file and writes a new file that contains just one sequence, with the original sequences catted together, preserving their order'''
      seq_reader = sequences.file_reader(infile)
      seqs = []
  
      for seq in seq_reader:
          seqs.append(copy.copy(seq))
  
      new_seq = ''.join([seq.seq for seq in seqs])
  
      if type(seqs[0]) == sequences.Fastq:
          new_qual = ''.join([seq.qual for seq in seqs])
          seqs[:] = []
          merged = sequences.Fastq(seqname, new_seq, new_qual)
      else:
          merged = sequences.Fasta(seqname, new_seq)
          seqs[:] = []
  
      f = utils.open_file_write(outfile)
      print(merged, file=f)
      utils.close(ff merge_to_one_seq(infile, outfile, seqname='union'):
      '''Takes a multi fasta or fastq file and writes a new file that contains just one sequence, with the original sequences catted together, preserving their order'''
      seq_reader = sequences.file_reader(infile)
      seqs = []
  
      for seq in seq_reader:
          seqs.append(copy.copy(seq))
  
      new_seq = ''.join([seq.seq for seq in seqs])
  
      if type(seqs[0]) == sequences.Fastq:
          new_qual = ''.join([seq.qual for seq in seqs])
          seqs[:] = []
          merged = sequences.Fastq(seqname, new_seq, new_qual)
      else:
          merged = sequences.Fasta(seqname, new_seq)
          seqs[:] = []
  
      f = utils.open_file_write(outfile)
      print(merged, file=f)
      utils.close(f)
docs: Takes a multi fasta or fastq file and writes a new file that contains just one sequence, with the original sequences catted together, preserving their order