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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 _check_field_names(self, field_names):
 """ Raises InvalidIndexError if any of a field_name in field_names is not indexed. """

        if field_names:
            for field_name in field_names:
                try:
                    self.column[field_name]
                except KeyError:
                    raise InvalidIndexError('Trying to use non indexed field "%s"' % field_name)