is_binary uses isinstance and inheritance

CHANGELOG-unreleased.md

@@ -20,6 +20,7 @@ the released changes.
 - Update CI tests for Python 3.12
 - Made `test_grid` routines faster
 - `pintk` uses downhill fitters by default
+- `is_binary` attribute now uses component inheritance
 ### Added
 - CHI2, CHI2R, TRES, DMRES now in postfit par files
 - Added `WaveX` model as a `DelayComponent` with Fourier amplitudes as fitted parameters

src/pint/models/timing_model.py

@@ -773,7 +773,10 @@ def phase_funcs(self):
     @property_exists
     def is_binary(self):
         """Does the model describe a binary pulsar?"""
-        return any(x.startswith("Binary") for x in self.components.keys())
+        # need to import here to avoid circular imports
+        from pint.models.pulsar_binary import PulsarBinary
+
+        return any(isinstance(x, PulsarBinary) for x in self.components.keys())
 
     def orbital_phase(self, barytimes, anom="mean", radians=True):
         """Return orbital phase (in radians) at barycentric MJD times.