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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def find_filter_class(filtername):
 """Lookup a filter by name. Return None if not found."""

    if filtername in FILTERS:
        return FILTERS[filtername]
    for name, cls in find_plugin_filters():
        if name == filtername:
            return cls
    return None