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