code: def v(p, r):
      """p = (p1, p2, p3); r = 0,1"""
      if r not in [1, 2]:
          raise ValueError("Value of r should lie between 1 and 2")
      p1, p2, p3 = p
      if r == 1:
          ksi = Matrix([[1], [0]])
      else:
          ksi = -Matrix([[0], [1]])
      a = (sigma1 * p1 + sigma2 * p2 + sigma3 * p3) / (E + m) * ksi
      if a == 0:
          a = zeros(2, 1)
      return sqrt(E + m) * Matrix(
          [[a[0, 0]], [a[1, 0]], [ksi[0, 0]], [ksi[1, 0]]]
      )
  
file_path: sympy/examples/advanced/qft.py
imports: from sympy import Basic, Symbol, Matrix, ones, sqrt, pprint, Eq, sympify
  from sympy.physics import msigma, mgamma
label_desc: Use image node_id 2 for calling a global function with example usage: v(p, r) and returns: unknown