code: def _nanaverage(a, weights=None):
      """Compute the weighted average, ignoring NaNs.
  
      Parameters
      ----------
      a : ndarray
          Array containing data to be averaged.
      weights : array-like, default=None
          An array of weights associated with the values in a. Each value in a
          contributes to the average according to its associated weight. The
          weights array can either be 1-D of the same shape as a. If `weights=None`,
          then all data in a are assumed to have a weight equal to one.
  
      Returns
      -------
      weighted_average : float
          The weighted average.
  
      Notes
      -----
      This wrapper to combine :func:`numpy.average` and :func:`numpy.nanmean`, so
      that :func:`np.nan` values are ignored from the average and weights can
      be passed. Note that when possible, we delegate to the prime methods.
      """
  
      if len(a) == 0:
          return np.nan
  
      mask = np.isnan(a)
      if mask.all():
          return np.nan
  
      if weights is None:
          return np.nanmean(a)
  
      weights = np.array(weights, copy=False)
      a, weights = a[~mask], weights[~mask]
      try:
          return np.average(a, weights=weights)
      except ZeroDivisionError:
          # this is when all weights are zero, then ignore them
          return np.average(a)
  
imports: import warnings
  import numpy
  from scipy import linalg, sparse
  from .None import check_random_state
  from ._array_api import _is_numpy_namespace, get_namespace
  from ._logistic_sigmoid import _log_logistic_sigmoid
  from .sparsefuncs_fast import csr_row_norms
  from .validation import check_array
label_desc: Use image node_id 19 for calling a global function with example usage: _nanaverage(a, weights) and returns: np, np, np, np, np