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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 _IsValidPath(message_descriptor, path):
 """Checks whether the path is valid for Message Descriptor."""

  parts = path.split('.')
  last = parts.pop()
  for name in parts:
    field = message_descriptor.fields_by_name[name]
    if (field is None or
        field.label == FieldDescriptor.LABEL_REPEATED or
        field.type != FieldDescriptor.TYPE_MESSAGE):
      return False
    message_descriptor = field.message_type
  return last in message_descriptor.fields_by_name