class_docstr: Exponential Linear Unit.
  
  It follows:
  
  ```
    f(x) =  alpha * (exp(x) - 1.) for x < 0
    f(x) = x for x >= 0
  ```
  
  Input shape:
    Arbitrary. Use the keyword argument `input_shape`
    (tuple of integers, does not include the samples axis)
    when using this layer as the first layer in a model.
  
  Output shape:
    Same shape as the input.
  
  Args:
    alpha: Scale for the negative factor.
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code: def call(self, inputs):
      return backend.elu(inputs, self.alpha)
  
imports: from tensorflow.python.framework import dtypes
  from tensorflow.python.keras import backend
  from tensorflow.python.keras import constraints
  from tensorflow.python.keras import initializers
  from tensorflow.python.keras import regularizers
  from tensorflow.python.keras.engine.base_layer import Layer
  from tensorflow.python.keras.engine.input_spec import InputSpec
  from tensorflow.python.keras.utils import tf_utils
  from tensorflow.python.ops import math_ops
label_desc: Use image node_id 2 for calling the ELU obj's underlying member method code with example usage: obj.call(inputs) and returns: backend