def get_missing_value_key(d):
    """
    Get the Missing Value entry from a table of data. If none is found, try the columns.
    If still none found, prompt user.

    :param dict d: Table of data
    :return str _mv: Missing Value
    """
    _mv = "nan"

    # Attempt to find a table-level missing value key
    try:
        # check for missing value key at the table root
        _mv = d["missingValue"]
    except KeyError as e:
        logger_misc.info("get_missing_value: No missing value key found: {}".format(e))
    except AttributeError as e:
        logger_misc.warn("get_missing_value: Column is wrong data type: {}".format(e))

    # No table-level missing value found. Attempt to find a column-level missing value key
    if not _mv:
        try:
            # loop for each column of data, searching for a missing value key
            for k, v in d["columns"].items():
                # found a column with a missing value key. Store it and exit the loop.
                _mv = v["missingValue"]
                break
        except KeyError:
            # There are no columns in this table. We've got bigger problems!
            pass

    # No table-level or column-level missing value. Out of places to look. Ask the user to enter the missing value
    # used in this data
    # if not _mv:
    #     print("No 'missingValue' key provided. Please type the missingValue used in this file: {}\n".format(filename))
    #     _mv = input("missingValue: ")
    return _mv
Get the Missing Value entry from a table of data. If none is found, try the columns.
    If still none found, prompt user.

    :param dict d: Table of data
    :return str _mv: Missing Value