code: def laplacian(expr):
      """
      Return the laplacian of the given field computed in terms of
      the base scalars of the given coordinate system.
  
      Parameters
      ==========
  
      expr : SymPy Expr or Vector
          expr denotes a scalar or vector field.
  
      Examples
      ========
  
      >>> from sympy.vector import CoordSys3D, laplacian
      >>> R = CoordSys3D('R')
      >>> f = R.x**2*R.y**5*R.z
      >>> laplacian(f)
      20*R.x**2*R.y**3*R.z + 2*R.y**5*R.z
      >>> f = R.x**2*R.i + R.y**3*R.j + R.z**4*R.k
      >>> laplacian(f)
      2*R.i + 6*R.y*R.j + 12*R.z**2*R.k
  
      """
  
      delop = Del()
      if expr.is_Vector:
          return (gradient(divergence(expr)) - curl(curl(expr))).doit()
      return delop.dot(delop(expr)).doit()
  
imports: from sympy.vector.coordsysrect import CoordSys3D
  from sympy.vector.deloperator import Del
  from sympy.vector.scalar import BaseScalar
  from sympy.vector.vector import Vector, BaseVector
  from sympy.vector.operators import gradient, curl, divergence
  from sympy.core.function import diff
  from sympy.core.singleton import S
  from sympy.integrals.integrals import integrate
  from sympy.simplify.simplify import simplify
  from sympy.core import sympify
  from sympy.vector.dyadic import Dyadic
label_desc: Use image node_id 3 for calling a global function with example usage: laplacian(expr) and returns: delop, unknown