code: def expm(C):
      r"""Exponential of SPD/HPD matrices.
  
      The symmetric matrix exponential of a SPD/HPD matrix
      :math:`\mathbf{C}` is defined by:
  
      .. math::
          \mathbf{D} = \mathbf{V} \exp{(\mathbf{\Lambda})} \mathbf{V}^H
  
      where :math:`\mathbf{\Lambda}` is the diagonal matrix of eigenvalues
      and :math:`\mathbf{V}` the eigenvectors of :math:`\mathbf{C}`.
  
      Parameters
      ----------
      C : ndarray, shape (..., n, n)
          SPD/HPD matrices, at least 2D ndarray.
  
      Returns
      -------
      D : ndarray, shape (..., n, n)
          Matrix exponential of C.
      """
      return _matrix_operator(C, np.exp)
  
file_path: pyRiemann/pyriemann/utils/base.py
imports: import numpy
  from numpy.core.numerictypes import typecodes
  from .test import is_pos_def
label_desc: Use image node_id 2 for calling a global function with example usage: expm(C) and returns: _matrix_operator