def is_transversion(self):
        """Is this variant a pyrimidine to purine change or vice versa"""
        return self.is_snv and is_purine(self.ref) != is_purine(self.alt)
def is_transversion ( self ) : return self . is_snv and is_purine ( self . ref ) != is_purine ( self . alt )
Is this variant a pyrimidine to purine change or vice versa