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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 getSampleTypeTitles(self):
 """Returns a list of sample type titles """

        sample_types = self.getSampleTypes()
        sample_type_titles = map(lambda obj: obj.Title(), sample_types)

        # N.B. This is used only for search purpose, because the catalog does
        #      not add an entry to the Keywordindex for an empty list.
        #
        # => This "empty" category allows to search for values with a certain
        #    sample type set OR with no sample type set.
        #    (see bika.lims.browser.analysisrequest.add2.get_sampletype_info)
        if not sample_type_titles:
            return [""]
        return sample_type_titles