code: def erf(x: np.ndarray) -> np.ndarray:
      # Using numerical recipes approximation for erf function
      # accurate to 1E-7
  
      ones = np.ones_like(x)
      zeros = np.zeros_like(x)
  
      t = ones / (ones + 0.5 * np.abs(x))
  
      coefficients = [
          1.00002368,
          0.37409196,
          0.09678418,
          -0.18628806,
          0.27886807,
          -1.13520398,
          1.48851587,
          -0.82215223,
          0.17087277,
      ]
  
      inner = zeros
      for c in coefficients[::-1]:
          inner = t * (c + inner)
  
      res = ones - t * np.exp(inner - 1.26551223 - np.square(x))
      return np.where(x >= zeros, res, -1.0 * res)
  
imports: from typing import Callable, Iterator, List, Optional, Tuple, Type
  import numpy
  from toolz import valmap
  from gluonts.core.component import validated, tensor_to_numpy
  from gluonts.dataset.common import DataEntry
  from gluonts.exceptions import assert_data_error
  from ._base import FlatMapTransformation, MapTransformation, SimpleTransformation
label_desc: Use image node_id 1 for calling a global function with example usage: erf(x) and returns: np