code: def close_holes(ref, Bc=None):
      """
      closed = close_holes(ref, Bc=None):
  
      Close Holes
  
      Parameters
      ----------
      ref : ndarray
          Reference image. This should be a binary image.
      Bc : structuring element, optional
          Default: 3x3 cross
  
      Returns
      -------
      closed : ndarray
          superset of `ref` (i.e. with closed holes)
      """
      _check_2(ref, "close_holes")
      ref = np.ascontiguousarray(ref, dtype=np.bool_)
      Bc = get_structuring_elem(ref, Bc)
      return _morph.close_holes(ref, Bc)
  
imports: from __future__ import division
  import numpy
  from .internal import _get_output, _verify_is_integer_type, _check_2
  from .None import _morph
label_desc: Use image node_id 11 for calling a global function with example usage: close_holes(ref, Bc) and returns: _morph