def get_gc_region(seqs, headers, positions):
    """
    Slice out the exact region of the fasta the primer amplified.
    Args:
        seqs (list): the list of sequences from flank_file
        headers (list): the list of headers from flank_file
        positions (list): list of tuples with header, p_len, p_seq
    Returns:
        sliced_seq (list): the exact amplified sequence.
    """
    sliced_seq = []
    for header, seq in zip(headers, seqs):
        for pos in positions:
            if pos[0] == header:
                sliced_seq.append((header, len(seq[pos[1]:pos[2]+1]), seq[pos[1]:pos[2]+1]))
    return sliced_seq