Computes the number of input and output units for a weight shape.

  Args:
    shape: Integer shape tuple or TF tensor shape.

  Returns:
    A tuple of scalars (fan_in, fan_out).

def _compute_fans(shape):
  """Computes the number of input and output units for a weight shape.

  Args:
    shape: Integer shape tuple or TF tensor shape.

  Returns:
    A tuple of scalars (fan_in, fan_out).
  """
  if len(shape) < 1:  # Just to avoid errors for constants.
    fan_in = fan_out = 1
  elif len(shape) == 1:
    fan_in = fan_out = shape[0]
  elif len(shape) == 2:
    fan_in = shape[0]
    fan_out = shape[1]
  else:
    # Assuming convolution kernels (2D, 3D, or more).
    # kernel shape: (..., input_depth, depth)
    receptive_field_size = 1.
    for dim in shape[:-2]:
      receptive_field_size *= dim
    fan_in = shape[-2] * receptive_field_size
    fan_out = shape[-1] * receptive_field_size
  if isinstance(fan_in, tf.Dimension):
    fan_in = fan_in.value
  if isinstance(fan_out, tf.Dimension):
    fan_out = fan_out.value
  return fan_in, fan_out