def combine_filters(collections, languages, preservations):
    """Make filter dictionary from user inputs.  Used to filter catalogue data.

    Args:
        collections (list of str): List of terms that should be ....
        languages (list of str):
        preservations (list of str):

    Return:
        filters (dict): Dictionary with keys equal to catalogue column names,
            values equal to list of strings that should be contained.
    """
    filters = {}

    if len(collections) > 0:
        filters['collection'] = collections

    if len(languages) > 0:
        filters['language'] = languages

    if len(preservations) > 0:
        filters['surface_preservation'] = preservations

    return filters