fileInput(inputId, label, multiple = FALSE, accept = NULL, width = NULL)input slot that will be used to access the value.NULL for no label.'400px', or '100%';
see validateCssUnit.actionButton,
checkboxGroupInput,
checkboxInput, dateInput,
dateRangeInput, numericInput,
passwordInput, radioButtons,
selectInput, sliderInput,
submitButton, textInput