Helper method for split_options which creates the options dict.
    Also handles the creation of a list for the URI tag_sets/
    readpreferencetags portion.

def _parse_options(opts, delim):
    """Helper method for split_options which creates the options dict.
    Also handles the creation of a list for the URI tag_sets/
    readpreferencetags portion."""
    options = {}
    for opt in opts.split(delim):
        key, val = opt.split("=")
        if key.lower() == 'readpreferencetags':
            options.setdefault('readpreferencetags', []).append(val)
        else:
            # str(option) to ensure that a unicode URI results in plain 'str'
            # option names. 'normalized' is then suitable to be passed as
            # kwargs in all Python versions.
            if str(key) in options:
                warnings.warn("Duplicate URI option %s" % (str(key),))
            options[str(key)] = unquote_plus(val)

    # Special case for deprecated options
    if "wtimeout" in options:
        if "wtimeoutMS" in options:
            options.pop("wtimeout")
        warnings.warn("Option wtimeout is deprecated, use 'wtimeoutMS'"
                      " instead")

    return options