"""Quote an argument for later parsing by shlex.split().

This function ensures that the argument is properly quoted so that it can be safely parsed by shlex.split(). 
The function checks for the presence of special characters (double quotes, single quotes, backslashes, and hash symbols) 
or spaces in the argument. If any of these are found, the argument is wrapped in quotes using Python's repr() function. 
Otherwise, the argument is returned as is.

Args:
    arg (str): The string argument to be quoted.

Returns:
    str: The quoted string if necessary, otherwise the original string.

Examples:
    >>> shquote('simple')
    'simple'
    >>> shquote('with spaces')
    "'with spaces'"
    >>> shquote('with"quote')
    "'with\"quote'"
    >>> shquote("with'quote")
    '"with\'quote"'
    >>> shquote('with\\backslash')
    "'with\\\\backslash'"
    >>> shquote('with#hash')
    "'with#hash'"
    >>> shquote('with spaces and"quote')
    "'with spaces and\"quote'"
    >>> shquote('0')
    '0'
    >>> shquote('Ī¸')
    'Ī¸'
"""