def source_type_normalize(source_type):
    """
    Make it easier to ignore small inconsistencies in these key word arguments.

    >>> source_type_normalize("journals")
    'journal'
    >>> source_type_normalize("Journal")
    'journal'

    """
    ret_val = None
    normal = {"journals": "journal",
              "videostreams": "videostream",
              "video": "videostream",
              "videos": "videostream",
              "books": "book"
              }
    if source_type is not None:
        source_type = source_type.lower()
        ret_val = normal.get(source_type, source_type)

    return ret_val