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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 item_meta(item_name, name, value, scheme=None):
 """ Adds meta information to an already defined item of the model being defined. @param item_name: name of the model item the meta data should be added to. @type item_name: str or unicode @param name: name of the meta data class @type name: str or unicode @param value: metadata value @type value: str or unicode @param scheme: format information about the value @type scheme: str or unicode or None """

    _annotate("item_meta", item_name, name, value, scheme=scheme)