def create_index_regex(input_symbol: str) -> str:
    """Creates a regular expression pattern to match the index symbology.

    To create the regular expression pattern, the function uses the fact that within the
    ICE consolidated feed, all the indices are identified by the root symbol (a unique
    mnemonic based on the exchange ticker or the ISIN), prefixed with the type.

    Parameters
    ----------
    input_symbol: str
        An index symbol consisting of the root symbol prefixed with the type identifier (I).

    Returns
    -------
    str
        The regular expression pattern that matches the index symbol passed as an input.
    """
    return rf"\b{input_symbol}\b"