Yields (line, line number) tuples from the given file handler. Skips
		the first line if the self.has_header flag is set.

		Helper for the gen_ipa_data method.

def _gen_txt_data(self, f):
		"""
		Yields (line, line number) tuples from the given file handler. Skips
		the first line if the self.has_header flag is set.

		Helper for the gen_ipa_data method.
		"""
		reader = iter(f)

		for line_num, line in enumerate(reader):
			if line_num == 0 and self.has_header:
				continue

			datum = line.rstrip('\r\n')

			yield datum, line_num+1