add information about identifier check
add information about string
add information about built-in functions of string module
add demo about unicode codec
add information about Unicode
add information about Unicode of Python
add information about list
add information about modules of sequence
add information about coping
add information about dictionary
add information about built-in function of dictionary
add information about key of dictionary
add information about set
add information about all function of sets
add information about list expression and generator expression
add information about built-in function of file object
add information about file object methods
add information about file attributes
add information about os.path and os module
add information about modules of file