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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def is_valid_note(note):
 """Return True if note is in a recognised format. False if not."""

    if not _note_dict.has_key(note[0]):
        return False
    for post in note[1:]:
        if post != 'b' and post != '#':
            return False
    return True