code: def _kappa_mle(x):
      mean = _circular_mean(x)
      kappa = _a1inv(np.mean(np.cos(x - mean)))
      return kappa
  
imports: import warnings
  import numpy
  from scipy.fftpack import fft
  from scipy.optimize import brentq
  from scipy.signal import convolve, convolve2d, gaussian
  from scipy.sparse import coo_matrix
  from scipy.special import ive
  from ..utils import _cov, _dot, _stack, conditional_jit
label_desc: Use image node_id 9 for calling a global function with example usage: _kappa_mle(x) and returns: kappa