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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 full_name(self):
 """Return the user's first name."""

        if self.first_name and self.middle_name and self.last_name:
            return "%s %s %s" % (self.first_name, self.middle_name, self.last_name)
        if self.first_name and self.last_name:
            return "%s %s" % (self.first_name, self.last_name)