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Here is an ad-hoc quick solution, hope it works for the special purpose needed:

def get_trigonometric_coefficients( A, x ):
    """A is the given trigonometric expression in a variable x.
    We extract the corresponding coefficients in sin(x)^k * cos(x)^n
    for possible k, n.
    """
    data_DIC = {}
    for op in A.operands():
        k, n = 0, 0
        # identify the type of the trigonometric expression appeared
        factors = op.factor_list()
        coeff   = 1
        for f, mul in factors:
            if f == sin(x):
                k += mul
            elif f == cos(x):
                n += mul
            else:
                coeff *= f^mul
        if (k,n) in data_DIC:
            data_DIC[ (k,n) ] += coeff
        else:
            data_DIC[ (k,n) ]  = coeff
        # print op, coeff, f, mul, '\n'
    keys = data_DIC.keys()
    keys . sort()
    return [ ( data_DIC[key], key ) for key in keys ]

# test
var( 'b1 b2 q x b3 b4 b5' );
A = b4*cos(x)^4 + (b2 + q)*cos(x)*sin(x)^2 + (b3/b1 + 6)*cos(x)*sin(x) + (b1 + 2)*sin(x) + b5
print get_trigonometric_coefficients( A, x )
print get_trigonometric_coefficients( A.expand(), x )

Results:

[(b5, (0, 0)), (b4, (0, 4)), (b1 + 2, (1, 0)), ((6*b1 + b3)/b1, (1, 1)), (b2 + q, (2, 1))]
[(b5, (0, 0)), (b4, (0, 4)), (b1 + 2, (1, 0)), (b3/b1 + 6, (1, 1)), (b2 + q, (2, 1))]