bitbake -- function document..

bitbake 一堆 conf, layer, bb 裡面用的語法，function，說明文件都在...source code 裡..
以 bb.utils.contains('DISTRO_FEATURES', 'wayland', 'west-init', '',d) 為例...
在 poky/bitbake/lib/bb/utils.py:

def contains(variable, checkvalues, truevalue, falsevalue, d):
    """Check if a variable contains all the values specified.

    Arguments:

    variable -- the variable name. This will be fetched and expanded (using
    d.getVar(variable, True)) and then split into a set().

    checkvalues -- if this is a string it is split on whitespace into a set(),
    otherwise coerced directly into a set().

    truevalue -- the value to return if checkvalues is a subset of variable.

    falsevalue -- the value to return if variable is empty or if checkvalues is
    not a subset of variable.

    d -- the data store.
    """