def __init__(self, initial_chords=None):
if initial_chords is None:<EOL><INDENT>initial_chords = []<EOL><DEDENT>if isinstance(initial_chords, Chord):<EOL><INDENT>self._chords = [initial_chords]<EOL><DEDENT>elif isinstance(initial_chords, str):<EOL><INDENT>self._chords = [as_chord(initial_chords)]<EOL><DEDENT>elif isinstance(initial_chords, list):<EOL><INDENT>self._chords = [as_chord(chord) for chord in initial_chords]<EOL><DEDENT>else:<EOL><INDENT>raise TypeError("<STR_LIT>".format(type(initial_chords)))<EOL><DEDENT>
Constructor of ChordProgression instance.

        :type initial_chords: str|pychord.Chord|list
        :param initial_chords: Initial chord or chords of the chord progressions