def extract_coordinates(map_location_series):
    """
    Helper to preprocess_enviro_df. Produces a dataframe of latitudes and
    longitudes.

    Inputs:
        - map_location_series: pandas series, contains strings, each
        containing (<latitude>, <longitude>) parts of the string
    Outputs:
        - lat_lon_extracted_df: pandas df, columns of latitudes and longitudes
    """
    # Extract ("lat", "long") part of the string and split into lat and long:
    lat_lon_extracted_df = map_location_series.str.extract(r'\((.*),(.*)\)')

    # Convert to float:
    lat_lon_extracted_df = lat_lon_extracted_df.astype(float)

    # Rename columns:
    lat_lon_extracted_df.columns = ["latitude", "longitude"]

    return lat_lon_extracted_df