def to_si(self, values, from_unit):
if from_unit in self.si_units:<EOL><INDENT>return values, from_unit<EOL><DEDENT>elif from_unit == '<STR_LIT>':<EOL><INDENT>return self.to_unit(values, '<STR_LIT>', from_unit), '<STR_LIT>'<EOL><DEDENT>elif from_unit == '<STR_LIT>':<EOL><INDENT>return self.to_unit(values, '<STR_LIT>', from_unit), '<STR_LIT>'<EOL><DEDENT>else:<EOL><INDENT>return self.to_unit(values, '<STR_LIT:m>', from_unit), '<STR_LIT:m>'<EOL><DEDENT>
Return values in SI and the units to which the values have been converted.