def format_cluster_markers_datatypes(df):
    """ specifies column types on cluster_markers_df before export """
    df['gene_symbol'] = df['gene_symbol'].astype(str)
    df['myAUC'] = df['myAUC'].astype(float)
    df['myDiff'] = df['myDiff'].astype(float)
    df['power'] = df['power'].astype(float)
    df['cluster_no'] = df['cluster_no'].astype(int)

    return df