code: def vstack(blocks, format=None, dtype=None):
      """Stacks sparse matrices vertically (row wise)
  
      Args:
          blocks (sequence of cupyx.scipy.sparse.spmatrix)
              sparse matrices to stack
          format (str, optional):
              sparse format of the result (e.g. "csr")
              by default an appropriate sparse matrix format is returned.
              This choice is subject to change.
          dtype (dtype, optional):
              The data-type of the output matrix.  If not given, the dtype is
              determined from that of `blocks`.
  
      Returns:
          cupyx.scipy.sparse.spmatrix: the stacked sparse matrix
  
      .. seealso:: :func:`scipy.sparse.vstack`
  
      Examples:
          >>> from cupy import array
          >>> from cupyx.scipy.sparse import csr_matrix, vstack
          >>> A = csr_matrix(array([[1., 2.], [3., 4.]]))
          >>> B = csr_matrix(array([[5., 6.]]))
          >>> vstack([A, B]).toarray()
          array([[1., 2.],
                 [3., 4.],
                 [5., 6.]])
      """
      return bmat([[b] for b in blocks], format=format, dtype=dtype)
  
file_path: cupy/cupyx/scipy/sparse/_construct.py
imports: import numpy
  import cupy
  from cupyx.scipy.sparse import _coo
  from cupyx.scipy.sparse import _csc
  from cupyx.scipy.sparse import _csr
  from cupyx.scipy.sparse import _dia
  from cupyx.scipy.sparse import _sputils
label_desc: Use image node_id 6 for calling a global function with example usage: vstack(blocks, format, dtype) and returns: bmat