class_docstr: Handle creating, starting and waiting for Amazon SageMaker jobs to finish.
  
  This class shouldn't be directly instantiated.
  
  Subclasses must define a way to create, start and wait for an Amazon
  SageMaker job.
class_docstr_tok: ["Handle","creating",",","starting","and","waiting","for","Amazon","SageMaker","jobs","to","finish",".","This","class","should","n't","be","directly","instantiated",".","Subclasses","must","define","a","way","to","create",",","start","and","wait","for","an","Amazon","SageMaker","job","."]
docstr: Placeholder docstring
docstr_tok: ["Placeholder","docstring"]
code: def _prepare_channel(
      input_config,
      channel_uri=None,
      channel_name=None,
      validate_uri=True,
      content_type=None,
      input_mode=None,
  ):
      """Placeholder docstring"""
      if not channel_uri:
          return None
      if not channel_name:
          raise ValueError(
              "Expected a channel name if a channel URI {} is specified".format(
                  channel_uri
              )
          )
  
      if input_config:
          for existing_channel in input_config:
              if existing_channel["ChannelName"] == channel_name:
                  raise ValueError(
                      "Duplicate channel {} not allowed.".format(
                          channel_name
                      )
                  )
  
      channel_input = _Job._format_string_uri_input(
          channel_uri, validate_uri, content_type, input_mode
      )
      channel = _Job._convert_input_to_channel(
          channel_name, channel_input
      )
  
      return channel
  
imports: from __future__ import absolute_import
  from abc import abstractmethod
  from six import string_types
  from sagemaker.inputs import FileSystemInput, TrainingInput
  from sagemaker.local import file_input
  from sagemaker.workflow import is_pipeline_variable
label_desc: Use image node_id 10 for calling the _Job obj's underlying member method code with example usage: obj._prepare_channel(input_config, channel_uri, channel_name, validate_uri, content_type, input_mode) and returns: channel, None