code: def _parse_linear_solver(linear_solver):
      """Helper function to retrieve a specified linear solver."""
      if callable(linear_solver):
          return linear_solver
      return lambda A, b: Matrix.solve(A, b, method=linear_solver)
  
imports: from sympy.utilities import dict_merge
  from sympy.utilities.iterables import iterable
  from sympy.physics.vector import Dyadic, Vector, ReferenceFrame, Point, dynamicsymbols
  from sympy.physics.vector.printing import vprint, vsprint, vpprint, vlatex, init_vprinting
  from sympy.physics.mechanics.particle import Particle
  from sympy.physics.mechanics.rigidbody import RigidBody
  from sympy.simplify.simplify import simplify
  from sympy import Matrix, Mul, Derivative, sin, cos, tan, S
  from sympy.core.function import AppliedUndef
  from sympy.physics.mechanics.inertia import inertia, inertia_of_point_mass
  from sympy.utilities.exceptions import sympy_deprecation_warning
label_desc: Use image node_id 20 for calling a global function with example usage: _parse_linear_solver(linear_solver) and returns: function, linear_solver