Takes in a list of PDB residue IDs (including insertion codes) specifying ranges and returns a sorted list of merged, sorted ranges.
       This works as above but we have to split the residues into pairs as  "1A" > "19".

def merge_pdb_range_pairs(prs):
    '''Takes in a list of PDB residue IDs (including insertion codes) specifying ranges and returns a sorted list of merged, sorted ranges.
       This works as above but we have to split the residues into pairs as  "1A" > "19".
    '''
    new_prs = []
    sprs = [sorted((split_pdb_residue(p[0]), split_pdb_residue(p[1]))) for p in prs]
    sprs = sorted(sprs)
    merged = False
    x = 0
    from klab import colortext
    while x < len(sprs):
        newx = x + 1
        new_pair = list(sprs[x])
        for y in range(x + 1, len(sprs)):
            if new_pair[0] <= (sprs[y][0][0] - 1, sprs[y][0][1]) <= new_pair[1]:
                new_pair[0] = min(new_pair[0], sprs[y][0])
                new_pair[1] = max(new_pair[1], sprs[y][1])
                newx = y + 1
        if new_pair not in new_prs:
            new_prs.append(new_pair)
        x = newx
    return new_prs