INTEGER dict_contains(DICTIONARY dict, ANY key)
This function returns 1 if there is an association in dict with the specified key, or 0 otherwise. Examples:
dict_contains(#[["foo", "bar"]], "foo")
=> 1
dict_contains(#[["foo", "bar"]], "bar")
=> 0
dict_add() | dict_contains() | dict_del() | dict_keys() | dict_union() | dict_values()