Encode this matrix in binary suitable for including in a PDF

def encode(self):
        """Encode this matrix in binary suitable for including in a PDF"""
        return '{:.6f} {:.6f} {:.6f} {:.6f} {:.6f} {:.6f}'.format(
            self.a, self.b, self.c, self.d, self.e, self.f
        ).encode()