class_docstr: Class for Stiefel manifolds St(n,p).
  
  A set of all orthonormal p-frames in n-dimensional space,
  where p <= n.
  
  Parameters
  ----------
  n : int
      Dimension of the ambient vector space.
  p : int
      Number of basis vectors in the orthonormal frame.
code: def _define_embedding_space(self):
      return Matrices(self.n, self.p)
  
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 Stiefel obj's underlying member method code with example usage: obj._define_embedding_space() and returns: Matrices