Sets the label (name) of signal edfsignal ("FP1", "SaO2", etc.).
edf_set_label(edf_handle, edfsignal, label)
: integer containing file handle of the opened bdf/edf-file
: Minimum value is 1
: string containing the label (name) of the signal edfsignal.
This function is recommended for every signal and can be called only after opening a file in writemode and before the first sample write action.