Applies a filter on a sequence of objects or looks up an attribute.
    This is useful when dealing with lists of objects but you are really
    only interested in a certain value of it.

    The basic usage is mapping on an attribute.  Imagine you have a list
    of users but you are only interested in a list of usernames:

    .. sourcecode:: jinja

        Users on this page: {{ users|map(attribute='username')|join(', ') }}

    Alternatively you can let it invoke a filter by passing the name of the
    filter and the arguments afterwards.  A good example would be applying a
    text conversion filter on a sequence:

    .. sourcecode:: jinja

        Users on this page: {{ titles|map('lower')|join(', ') }}

    .. versionadded:: 2.7

def do_map(*args, **kwargs):
    """Applies a filter on a sequence of objects or looks up an attribute.
    This is useful when dealing with lists of objects but you are really
    only interested in a certain value of it.

    The basic usage is mapping on an attribute.  Imagine you have a list
    of users but you are only interested in a list of usernames:

    .. sourcecode:: jinja

        Users on this page: {{ users|map(attribute='username')|join(', ') }}

    Alternatively you can let it invoke a filter by passing the name of the
    filter and the arguments afterwards.  A good example would be applying a
    text conversion filter on a sequence:

    .. sourcecode:: jinja

        Users on this page: {{ titles|map('lower')|join(', ') }}

    .. versionadded:: 2.7
    """
    seq, func = prepare_map(args, kwargs)
    if seq:
        for item in seq:
            yield func(item)