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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 _emp_extra_options(options):
 """ Get special options patch, cols, and splits if analysis in emp module """


    # Check that metadata is valid
    metadata_path = os.path.normpath(os.path.join(options['param_dir'],
                                                  options['metadata']))
    if not os.path.isfile(metadata_path):
        raise IOError, ("Path to metadata file %s is invalid." %
                        metadata_path)
    options['metadata_path'] = metadata_path

    # Using subset if given, create and store patch
    subset = options.get('subset', '')
    options['patch'] = emp.Patch(metadata_path, subset)

    # If cols or splits not given in options, make empty strings
    if 'cols' not in options.keys():
        options['cols'] = ''
    if 'splits' not in options.keys():
        options['splits'] = ''

    return options