TypeError: __init__() missing 1 required positional argument: 'ref_rotation'

[JBrame]

Firstly, thanks for creating and sharing the library, it looks like something that might be really useful to me.

However, I have just tried to use it and the there isn't any documentation around the parameter ref_rotation.

The code states:

    To initialize, pass 6 parameters
    r_B = Radius for circumscribed circle where all the anchor points for servo shaft lie on
    r_P = Radius for circumscribed circle where all anchor points for platform lie on
    lhl = |h| = length of servo horn
    ldl = |d| = length of rod
    alpha_B =
    alpha_P =

Yet the function takes 7 parameters and there is no default for ref_rotation: def __init__(s, r_B, r_P, lhl, ldl, gamma_B, gamma_P, ref_rotation)

Can you tell me what ref_rotation is and how it should be used please?