code: def linear_momentum(frame, *body):
      """Linear momentum of the system.
  
      Explanation
      ===========
  
      This function returns the linear momentum of a system of Particle's and/or
      RigidBody's. The linear momentum of a system is equal to the vector sum of
      the linear momentum of its constituents. Consider a system, S, comprised of
      a rigid body, A, and a particle, P. The linear momentum of the system, L,
      is equal to the vector sum of the linear momentum of the particle, L1, and
      the linear momentum of the rigid body, L2, i.e.
  
      L = L1 + L2
  
      Parameters
      ==========
  
      frame : ReferenceFrame
          The frame in which linear momentum is desired.
      body1, body2, body3... : Particle and/or RigidBody
          The body (or bodies) whose linear momentum is required.
  
      Examples
      ========
  
      >>> from sympy.physics.mechanics import Point, Particle, ReferenceFrame
      >>> from sympy.physics.mechanics import RigidBody, outer, linear_momentum
      >>> N = ReferenceFrame('N')
      >>> P = Point('P')
      >>> P.set_vel(N, 10 * N.x)
      >>> Pa = Particle('Pa', P, 1)
      >>> Ac = Point('Ac')
      >>> Ac.set_vel(N, 25 * N.y)
      >>> I = outer(N.x, N.x)
      >>> A = RigidBody('A', Ac, N, 20, (I, Ac))
      >>> linear_momentum(N, A, Pa)
      10*N.x + 500*N.y
  
      """
  
      if not isinstance(frame, ReferenceFrame):
          raise TypeError("Please specify a valid ReferenceFrame")
      else:
          linear_momentum_sys = Vector(0)
          for e in body:
              if isinstance(e, (RigidBody, Particle)):
                  linear_momentum_sys += e.linear_momentum(frame)
              else:
                  raise TypeError(
                      "*body must have only Particle or RigidBody"
                  )
      return linear_momentum_sys
  
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 4 for calling a global function with example usage: linear_momentum(frame) and returns: linear_momentum_sys