The function ch4_prod.py should be downloading an Input file for biogas feed-in Biogaspartner_Einspeiseatlas_Deutschland_2021.xls.
The associated website, from which the file is downloaded, doesn't exist anymore. The old Link to the website: https://www.dena.de/biogaspartner/fileadmin/Biogaspartner/Dokumente/Einspeiseatlas/Biogaspartner_Einspeiseatlas_Deutschland_2021.xlsx
Current workaround: Just copy the file Biogaspartner_Einspeiseatlas_Deutschland_2021.xls from another instance into the right data path.