quantizationtools.is_valid_beatspan

abjad.tools.quantizationtools.is_valid_beatspan.is_valid_beatspan(beatspan)

True if beatspan is a valid beatspan.

1. A beatspan must be an int or Fraction.

2. It must be a binary rational.

3. If it is greater than zero, it must be a power of two.

4. If it is less than zero, it must be Fraction, whose numerator is 1

   and whose denominator is a power of two.