code: def prepare_inputs(source_path, use_tpu=False, num_readers=None):
      """Return a tf.data input_fn from the source_path.
  
      Args:
        source_path: Path to a TFRecord file containing deepvariant tf.Example
          protos.
        use_tpu: boolean.  Use the tpu code path.
        num_readers: int > 0 or None. Number of parallel readers to use to read
          examples from source_path. If None, uses FLAGS.num_readers instead.
  
      Returns:
        A tf input_fn yielding batches of image, encoded_variant,
        encoded_alt_allele_indices.
  
        The image is a [batch_size, height, width, channel] tensor. The
        encoded_variants is a tf.string or tpu-encoded tensor containing a
        serialized Variant proto describing the variant call associated with
        image. The encoded_alt_allele_indices is a tf.string or tpu-encoded
        tensor containing a serialized CallVariantsOutput.AltAlleleIndices proto
        containing the alternate alleles indices used as "alt" when constructing
        the image.
      """
      if not num_readers:
          num_readers = FLAGS.num_readers
  
      return data_providers.get_input_fn_from_filespec(
          input_file_spec=source_path,
          mode=tf_estimator.ModeKeys.PREDICT,
          use_tpu=use_tpu,
          input_read_threads=num_readers,
          debugging_true_label_mode=FLAGS.debugging_true_label_mode,
      )
  
imports: import os
  import time
  from absl import flags
  from absl import logging
  import numpy
  import tensorflow
  from tensorflow import estimator
  from deepvariant import data_providers
  from deepvariant import dv_utils
  from deepvariant import logging_level
  from deepvariant import modeling
  from deepvariant.protos import deepvariant_pb2
  from google.protobuf import text_format
  from third_party.nucleus.io import sharded_file_utils
  from third_party.nucleus.io import tfrecord
  from third_party.nucleus.protos import variants_pb2
  from third_party.nucleus.util import errors
  from third_party.nucleus.util import proto_utils
  from third_party.nucleus.util import variant_utils
label_desc: Use image node_id 1 for calling a global function with example usage: prepare_inputs(source_path, use_tpu, num_readers) and returns: data_providers