class_docstr: This transform works for each ``const`` op if:
  
  - ``_is_deprecated=True`` and the ``op_selector`` returns ``True``.
  - ``_is_deprecated=False`` and the ``const`` value size ``> weight_threshold``.
  
  The transform performs the following:
  
  - The fraction of values with the least absolute value are zeroed out (self.sparsity).
  - If ``fake_compression=False``, the zeroed-out value is encoded using the ``constexpr_sparse_to_dense`` op.
  - If ``fake_compression=True``, the zeroed-out value is encoded using the ``const`` op.
  - Old ``const`` is replaced by a new operation with zeroed-out value.
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code: def compress_by_threshold(
      val, threshold, minimum_sparsity_percentile
  ):
      val = np.where(np.abs(val) <= threshold, 0, val)
      sparsity_percentile = np.sum(val == 0.0) / val.size
      if sparsity_percentile < minimum_sparsity_percentile:
          msg = (
              f"weight value has sparsity of {sparsity_percentile} < "
              f"minimum_sparsity_percentile {minimum_sparsity_percentile}. Skipped."
          )
          logger.warning(msg)
          return None
      return prune_weights._pack_val_to_sparse_param(val)
  
imports: from typing import Callable, Optional, Tuple
  import numpy
  from tqdm import tqdm
  from coremltools import _logger
  from coremltools.converters.mil._deployment_compatibility import AvailableTarget
  from coremltools.converters.mil.backend.mil.load import should_use_weight_file
  from coremltools.converters.mil.mil import Builder
  from coremltools.converters.mil.mil import Operation, Program, types
  from coremltools.converters.mil.mil.block import is_current_opset_version_compatible_with
  from coremltools.converters.mil.mil.ops.defs._utils import pack_elements_into_bits
  from coremltools.converters.mil.mil.ops.defs.iOS16 import constexpr_affine_dequantize, constexpr_lut_to_dense, constexpr_sparse_to_dense
  from coremltools.converters.mil.mil.passes.defs.quantization import AbstractQuantizationPass
  from coremltools.converters.mil.mil.passes.helper import block_context_manager
  from coremltools.converters.mil.mil.passes.pass_registry import register_pass
  from coremltools.converters.mil.mil.types.type_mapping import nptype_from_builtin
  from coremltools.models.neural_network.quantization_utils import _get_kmeans_lookup_table_and_weight
  from coremltools.optimize.coreml._config import OpLinearQuantizerConfig, OpMagnitudePrunerConfig, OpPalettizerConfig, OpThresholdPrunerConfig, OptimizationConfig
label_desc: Use image node_id 3 for calling the prune_weights obj's underlying member method code with example usage: obj.compress_by_threshold(val, threshold, minimum_sparsity_percentile) and returns: prune_weights, None