"{}"
"{:08d}"
"{0:d}"
"{0:x}"
"{0:o}"
"{0:b}"
"{:03.2f}"
"{1}"
"{0}"
"{:<8}"
"{:<999999999999999999999999}"
"[%H:%M:%S %z]"
"[%^%L%$]"
"[thread %t]"
"%v"
"%+"
"{:X}"
"{:s}"
"{:p}"
"{:n}"