Add bind() method to MjModel and MjData.

This method allows users to bind a spec to a model or data object, making it less verbose to access its arrays.

PiperOrigin-RevId: 699952211
Change-Id: I6b71a88d5a6968bc0f902bd49db7c568b46a4dfb

python/mujoco/indexer_xmacro.h

@@ -307,6 +307,28 @@
   XGROUP( MjModelTupleViews,    tuple,    ntuple,   MJMODEL_TUPLE    ) \
   XGROUP( MjModelKeyframeViews, key,      nkey,     MJMODEL_KEYFRAME )
 
+#define MJMODEL_BIND_GROUPS      \
+  XGROUP( mjsActuator, actuator) \
+  XGROUP( mjsBody,     body    ) \
+  XGROUP( mjsCamera,   cam     ) \
+  XGROUP( mjsEquality, eq      ) \
+  XGROUP( mjsExclude,  exclude ) \
+  XGROUP( mjsGeom,     geom    ) \
+  XGROUP( mjsHField,   hfield  ) \
+  XGROUP( mjsJoint,    jnt     ) \
+  XGROUP( mjsLight,    light   ) \
+  XGROUP( mjsMaterial, mat     ) \
+  XGROUP( mjsMesh,     mesh    ) \
+  XGROUP( mjsNumeric,  numeric ) \
+  XGROUP( mjsPair,     pair    ) \
+  XGROUP( mjsSensor,   sensor  ) \
+  XGROUP( mjsSite,     site    ) \
+  XGROUP( mjsSkin,     skin    ) \
+  XGROUP( mjsTendon,   tendon  ) \
+  XGROUP( mjsTexture,  tex     ) \
+  XGROUP( mjsTuple,    tuple   ) \
+  XGROUP( mjsKey,      key     )
+
 #define MJMODEL_VIEW_GROUPS_ALTNAMES        \
   XGROUP( cam, camera,   MJMODEL_CAMERA   ) \
   XGROUP( eq,  equality, MJMODEL_EQUALITY ) \
@@ -399,6 +421,17 @@
   XGROUP( MjDataSiteViews,     site,     nsite,    MJDATA_SITE     ) \
   XGROUP( MjDataTendonViews,   tendon,   ntendon,  MJDATA_TENDON   )
 
+#define MJDATA_BIND_GROUPS       \
+  XGROUP( mjsActuator, actuator) \
+  XGROUP( mjsBody,     body    ) \
+  XGROUP( mjsCamera,   cam     ) \
+  XGROUP( mjsGeom,     geom    ) \
+  XGROUP( mjsJoint,    jnt     ) \
+  XGROUP( mjsLight,    light   ) \
+  XGROUP( mjsSensor,   sensor  ) \
+  XGROUP( mjsSite,     site    ) \
+  XGROUP( mjsTendon,   tendon  )
+
 #define MJDATA_VIEW_GROUPS_ALTNAMES       \
   XGROUP( cam,    camera, MJDATA_CAMERA ) \
   XGROUP( jnt,    joint,  MJDATA_JOINT  ) \