code: def erf(x):
      """
      erf of a real number.
      """
      x = float(x)
      if x != x:
          return x
      if x < 0.0:
          return -erf(-x)
      if x >= 1.0:
          if x >= 6.0:
              return 1.0
          return 1.0 - _erfc_mid(x)
      return _erf_taylor(x)
  
imports: import operator
  import math
  import cmath
label_desc: Use image node_id 23 for calling a global function with example usage: erf(x) and returns: _erf_taylor, x, unknown, unknown, int