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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 add_string_pairs_from_label_element(xib_file, results, label, special_ui_components_prefix):
 """ Adds string pairs from a label element. Args: xib_file (str):
 Path to the xib file. results (list):
 The list to add the results to. label (element):
 The label element from the xib, to extract the string pairs from. special_ui_components_prefix (str):
 If not None, extraction will not warn about internationalized UI components with this class prefix. """

    label_entry_comment = extract_element_internationalized_comment(label)
    if label_entry_comment is None:
        return

    warn_if_element_not_of_class(label, 'Label', special_ui_components_prefix)

    if label.hasAttribute('usesAttributedText') and label.attributes['usesAttributedText'].value == 'YES':
        add_string_pairs_from_attributed_ui_element(results, label, label_entry_comment)
    else:
        try:
            label_entry_key = label.attributes['text'].value
        except KeyError:
            try:
                label_entry_key = label.getElementsByTagName('string')[0].firstChild.nodeValue
            except Exception:
                label_entry_key = 'N/A'
                logging.warn("%s: Missing text entry in %s", xib_file, label.toxml('UTF8'))
        results.append((label_entry_key, label_entry_comment))