docstr: Shift an array's content forward by 1 time step along the first axis,
  keeping the shape identical by padding on the left with zeros.
  
  Parameters
  ----------
  A : nd.NDArray
      Shape (N, T, ...), the tensor in which the entries will be shifted
      forward by one
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code: def forwardshift(A):
      """
      Shift an array's content forward by 1 time step along the first axis,
      keeping the shape identical by padding on the left with zeros.
  
      Parameters
      ----------
      A : nd.NDArray
          Shape (N, T, ...), the tensor in which the entries will be shifted
          forward by one
      """
      F = getF(A)
      A = F.Concat(
          F.zeros_like(F.slice_axis(A, axis=1, begin=0, end=1)),
          A,
          dim=1,
      )
      return F.slice_axis(A, axis=1, begin=0, end=-1)
  
imports: from typing import Optional, Tuple
  import mxnet
  from gluonts.core.component import validated
  from gluonts.mx import Tensor
  from gluonts.mx.distribution import Distribution, DistributionOutput
  from gluonts.mx.distribution.distribution import getF
  from mxnet import gluon
label_desc: Use image node_id 4 for calling the DeepRenewalNetwork obj's underlying member method code with example usage: obj.forwardshift(A) and returns: F