add_no_selected_choices
                        Add empty choice to choices selected
check_no_multiple_selection
                        Checks that the 'extract_input' specification
                        does not allow multiple selection
choices_labeled         Set "<choice>:<label>" type of names
choices_selected        Choices selected
compose_and_enable_validators
                        Function to compose 'validators' from
                        'data_extract_multiple_srv'
data_extract_multiple_srv
                        Creates a named list of 'data_extract_srv'
                        output
data_extract_spec       Data extract input for 'teal' modules
data_extract_srv        Extraction of the selector(s) details
data_extract_ui         'teal' data extraction module user-interface
datanames_input         Help text with available datasets input
delayed_choices         Bare constructor for 'delayed_choices' object
filter_spec             Data extract filter specification
format_data_extract     Formatting data extracts
get_anl_relabel_call    Gets the relabel call
get_dataset_prefixed_col_names
                        Returns non-key column names from data
get_extract_datanames   Gets names of the datasets from a list of
                        'data_extract_spec' objects
get_merge_call          Get merge call from a list of selectors
get_relabel_call        Create relabel call from named character
is_single_dataset       Verify uniform dataset source across data
                        extract specification
list_extract_spec       Make sure that the extract specification is in
                        list format
merge_datasets          Merge the datasets on the keys
merge_expression_module
                        Merge expression module
merge_expression_srv    Data merge module server
no_selected_as_NULL     Check select choices for no choice made
resolve_delayed         Resolve delayed inputs by evaluating the code
                        within the provided datasets
select_spec             Column selection input specification
split_by_sep            Split by separator (matched exactly)
value_choices           Value labeling and filtering based on variable
                        relationship
variable_choices        Variable label extraction and custom selection
                        from data
