code: def vstack(arrs):
      """
      Stack arrays in sequence vertically (row wise).
      1-D arrays of shape `(N,)`, will reshaped to `(1,N)` before concatenation.
      For all other arrays, equivalent to  :func:`.concatenate` with axis=0.
  
      Examples
      --------
      >>> a = hl.nd.array([1, 2, 3])
      >>> b = hl.nd.array([2, 3, 4])
      >>> hl.eval(hl.nd.vstack((a,b)))
      array([[1, 2, 3],
             [2, 3, 4]], dtype=int32)
      >>> a = hl.nd.array([[1], [2], [3]])
      >>> b = hl.nd.array([[2], [3], [4]])
      >>> hl.eval(hl.nd.vstack((a,b)))
      array([[1],
             [2],
             [3],
             [2],
             [3],
             [4]], dtype=int32)
  
      Parameters
      ----------
      arrs : sequence of :class:`.NDArrayExpression`
          The arrays must have the same shape along all but the first axis.
          1-D arrays must have the same length.
  
      Returns
      -------
      :class:`.NDArrayExpression`
          The array formed by stacking the given arrays, will be at least 2-D.
  
      See Also
      --------
      :func:`.concatenate` : Join a sequence of arrays along an existing axis.
  
      """
      head_ndim = arrs[0].ndim
  
      if head_ndim == 1:
          return concatenate(hl.map(lambda a: a._broadcast(2), arrs), 0)
  
      return concatenate(arrs, 0)
  
imports: from functools import reduce
  import hail
  from hail.expr.functions import _ndarray
  from hail.expr.functions import array
  from hail.expr.types import HailType, tfloat64, tfloat32, ttuple, tndarray
  from hail.typecheck import typecheck, nullable, oneof, tupleof, sequenceof
  from hail.expr.expressions import expr_int32, expr_int64, expr_tuple, expr_any, expr_array, expr_ndarray, expr_numeric, Int64Expression, cast_expr, construct_expr, expr_bool, unify_all
  from hail.expr.expressions.typed_expressions import NDArrayNumericExpression
  from hail.ir import NDArrayQR, NDArrayInv, NDArrayConcat, NDArraySVD, NDArrayEigh, Apply
label_desc: Use image node_id 18 for calling a global function with example usage: vstack(arrs) and returns: concatenate, concatenate