from typing import List


def list_to_str(gene_list: List[str]) -> str:
    """Transform list of genes into a large string separated by comma to
    feed reactome2py identifiers function

    Args:
        gene_list: List of genes short-names

    Returns:
        Large string with all genes short-names separated by comma

    """
    genes_str = ""
    for gene in gene_list:
        genes_str = genes_str + "," + gene
    return genes_str[1:]