def isValidAssocExtn(extname):
    """
    Determine if the extension name given as input could
    represent a valid association file.

    Parameters
    ----------
    extname : string

    Returns
    -------
    isValid  : boolean value

    """
    # Define a list of valid extension types to define an association table.
    validExtnNames = ['asn','asc']

    # Loop over the list of valid extension types and compare with the input
    # extension name.  If there is ever a match return True.
    for validName in validExtnNames:
        if (extname == validName):
            return True
    return False