<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def exclude_sources(exclude, section=False):
 """ Returns a narrower list of sources. If the exclude parameter is a list, every one of its items will be removed from the returned list. If it's just a function (or a function's name) and 'section' is set to False (default), a copy of the sources list without this element will be returned. If it's a function (or a function's name) but the section parameter is set to True, the returned list will be a section of the sources list, including everything between 'exclude' and the end of the list. """

    newlist = sources.copy()
    if not isinstance(exclude, list):
        exclude = [exclude]

    for source in exclude:
        if not section:
            newlist.remove(source)
        else:
            pos = newlist.index(source) + 1
            if pos == len(sources):
                return []
            newlist = sources[pos:]
    return newlist