code: def _slope(y, axis=0):
      """Find the slope for each series of y.
  
      Parameters
      ----------
      y: np.ndarray
          Time series
      axis : int, optional (default=0)
          Axis along which to compute slope
  
      Returns
      -------
      slope : np.ndarray
          Time series slope
      """
      # Make sure y is always at least 2-dimensional
      if y.ndim == 1:
          y = y.reshape(-1, 1)
  
      # Generate time index with correct shape for broadcasting
      shape = np.ones(y.ndim, dtype=int)
      shape[axis] *= -1
      x = np.arange(y.shape[axis]).reshape(shape) + 1
  
      # Precompute mean
      x_mean = x.mean()
  
      # Compute slope along given axis
      return (
          np.mean(y * x, axis=axis) - x_mean * np.mean(y, axis=axis)
      ) / ((x * x).mean() - x_mean**2)
  
label_desc: Use image node_id 2 for calling a global function with example usage: _slope(y, axis) and returns: unknown