pose: This is the pose of the inertial reference frame, relative
to the link reference frame. The origin of the inertial
reference frame needs to be at the center of gravity. The
axes of the inertial reference frame do not need to be
aligned with the principal axes of the inertia.
inertia: The 3x3 rotational inertia matrix. Because the
rotational inertia matrix is symmetric, only 6 above-
diagonal elements of this matrix are specified here, using
the attributes ixx, ixy, ixz, iyy, iyz, izz.
Note that only complex elements are listed here. Elements that resolve to simple
types (int, str, bool) are inlined.