docstr: Orthogonal matrix completion.
  
  Parameters
  ----------
  matrix_m : array-like
  matrix_n : array-like
  
  Returns
  -------
  matrix_v : array-like
code: def _orthogonal_completion(matrix_m, matrix_n):
      """Orthogonal matrix completion.
  
      Parameters
      ----------
      matrix_m : array-like
      matrix_n : array-like
  
      Returns
      -------
      matrix_v : array-like
      """
      matrix_w = gs.concatenate([matrix_m, matrix_n], axis=-2)
      matrix_v, _ = gs.linalg.qr(matrix_w, mode="complete")
  
      return matrix_v
  
imports: import warnings
  import geomstats.backend
  import geomstats.errors
  from geomstats import algebra_utils
  from geomstats.geometry.base import LevelSet
  from geomstats.geometry.hermitian_matrices import powermh
  from geomstats.geometry.matrices import Matrices
  from geomstats.geometry.riemannian_metric import RiemannianMetric
  from geomstats.vectorization import repeat_out
label_desc: Use image node_id 3 for calling the _StiefelLogSolver obj's underlying member method code with example usage: obj._orthogonal_completion(matrix_m, matrix_n) and returns: matrix_v