move rigid_id property to abstract_site from atom, write out rigid_id…

… in to_mbuild

gmso/abc/abstract_site.py

@@ -209,6 +209,12 @@ class Site(GMSOBase):
         alias="position",
     )
 
+    rigid_id_: Optional[int] = Field(
+        None,
+        description="Rigid body ID used to assign rigid body contraints in HOOMD-Blue topologies.",
+        alias="rigid_id",
+    )
+
     model_config = ConfigDict(
         alias_to_fields={
             "name": "name_",
@@ -250,6 +256,11 @@ def residue(self):
         """Return the residue assigned to the site."""
         return self.__dict__.get("residue_")
 
+    @property
+    def rigid_id(self):
+        """Return the rigid body ID for this atom."""
+        return self.__dict__.get("rigid_id_")
+
     @field_serializer("position_")
     def serialize_position(self, position_: PositionType):
         return unyt_to_dict(position_)

gmso/core/atom.py

@@ -73,12 +73,6 @@ class Atom(Site):
         alias="restraint",
     )
 
-    rigid_id_: Optional[int] = Field(
-        None,
-        description="Rigid body ID used to assign rigid body contraints in HOOMD-Blue topologies.",
-        alias="rigid_id",
-    )
-
     model_config = ConfigDict(
         alias_to_fields=dict(
             **Site.model_config["alias_to_fields"],
@@ -131,11 +125,6 @@ def restraint(self):
         """Return the restraint of this atom."""
         return self.__dict__.get("restraint_")
 
-    @property
-    def rigid_id(self):
-        """Return the rigid body ID for this atom."""
-        return self.__dict__.get("rigid_id_")
-
     @field_serializer("charge_")
     def serialize_charge(self, charge_: Union[u.unyt_quantity, None]):
         if charge_ is None:

gmso/external/convert_mbuild.py

@@ -251,6 +251,7 @@ def _parse_particle(particle_map, site):
         charge=charge,
         mass=mass,
     )
+    particle.rigid_id = site.rigid_id
     particle_map[site] = particle
     return particle