<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _mergeProteinEntries(proteinLists, protToPeps):
 """Returns a new "protToPeps" dictionary with entries merged that are present in proteinLists. NOTE: The key of the merged entry is a tuple of the sorted protein keys. This behaviour might change in the future; the tuple might be replaced by simply one of the protein entries which is then representative for all. :param proteinLists: a list of protein groups that will be merged :param protToPeps: dict, for each protein (=key) contains a set of """

    mergedProtToPeps = dict(protToPeps)
    for proteins in proteinLists:
        for protein in proteins:
            peptides = mergedProtToPeps.pop(protein)
        mergedProtein = tuple(sorted(proteins))
        mergedProtToPeps[mergedProtein] = peptides
    return mergedProtToPeps