code: def cdf(x, mu, sigma):
      """Return the cumulative density function as an expression in x"""
      # x = sy.sympify(x)
      return (1 + sy.erf((x - mu) / (sigma * sy.sqrt(2)))) / 2
  
label_desc: Use image node_id 2 for calling a global function with example usage: cdf(x, mu, sigma) and returns: unknown