def is_protein_package(self):
if not hasattr(self, '<STR_LIT>'):<EOL><INDENT>self._is_protein_package = GraftMPackageVersion3.graftm_package_is_protein(self)<EOL><DEDENT>return self._is_protein_package<EOL>
Return true if this package is an Amino Acid alignment package, otherwise
        False i.e. it is a nucleotide package. Cache the result for speed.