<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def renderer_doc(*args):
    '''
    Return the docstrings for all renderers. Optionally, specify a renderer or a
    function to narrow the selection.

    The strings are aggregated into a single document on the master for easy
    reading.

    Multiple renderers can be specified.

    .. versionadded:: 2015.5.0

    CLI Example:

    .. code-block:: bash

        salt '*' sys.renderer_doc
        salt '*' sys.renderer_doc cheetah
        salt '*' sys.renderer_doc jinja json

    Renderer names can be specified as globs.

    .. code-block:: bash

        salt '*' sys.renderer_doc 'c*' 'j*'

    '''
    renderers_ = salt.loader.render(__opts__, [])
    docs = {}
    if not args:
        for func in six.iterkeys(renderers_):
            docs[func] = renderers_[func].__doc__
        return _strip_rst(docs)

    for module in args:
        if '*' in module or '.' in module:
            for func in fnmatch.filter(renderers_, module):
                docs[func] = renderers_[func].__doc__
        else:
            moduledot = module + '.'
            for func in six.iterkeys(renderers_):
                if func.startswith(moduledot):
                    docs[func] = renderers_[func].__doc__
    return _strip_rst(docs)