def require_amount_dimension(mapping):
    """ Each mapping needs to have a amount dimension. """
    if 'amount' not in mapping.keys():
        return "Mapping does not contain an amount measure." \
                "At least this measure must exist and contain " \
                "the key value of this entry."
    # TODO: in the future, this should check 'type':
    if mapping['amount'].get('datatype') != 'float':
        return "The amount must be a numeric the datatype " \
                "(i.e. 'float') to be a valid measure."
    return True
def require_time_dimension(mapping):
    """ Each mapping needs to have a time dimension. """
    if 'time' not in mapping.keys():
        return "Mapping does not contain a time dimension." \
                "The dimension must exist and contain a date " \
                "to describe the entry."
    # TODO: in the future, this should check 'type':
    if mapping['time'].get('datatype') != 'date':
        return "The 'time' dimension must have the datatype " \
                "'date' as it will be converted to a date " \
                "dimension."
    return True