def _split_columns(entry, split_list):
    """
    split pre-defined dictionary entries along pre-defined separators
    args:
        entry: a bibliography entry
        split_list: a pre-defined list of columns to separate
    returns:
        entry: the split entry
    """

    # function to strip trailing spaces
    space_stripper = lambda x: x.rstrip().lstrip()

    # iterate over pre-defined split_list
    for label, separator in split_list.items():
        try:
            entry[label] = space_stripper(entry[label]).rstrip(';')
            entry[label] = entry[label].split(separator)
            entry[label] = list(
                map(space_stripper, entry[label])
            )
        except:
            continue
    
    return entry