Get special options patch, cols, and splits if analysis in emp module

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