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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def remove_padding(sequence):
 """Selects the used frames of a sequence, up to its length. This function does not expect a batch of sequences, but a single sequence. The sequence must be a dict with `length` key, which will removed from the result. Args: sequence: Nested dict of tensors with time dimension. Returns: Nested dict of tensors with padding elements and `length` key removed. """

  length = sequence.pop('length')
  sequence = tools.nested.map(lambda tensor: tensor[:length], sequence)
  return sequence