def METHOD_NAME (qw, qx, qy, qz):
    '''
    Translates from Quaternion to Roll. 
    @param qw,qx,qy,qz: Quaternion values
    @type qw,qx,qy,qz: float
    @return Roll value translated from Quaternion
    '''
    rotateXa0=2.0*(qy*qz + qw*qx)
    rotateXa1=qw*qw - qx*qx - qy*qy + qz*qz
    rotateX=0.0
    if(rotateXa0 != 0.0 and rotateXa1 != 0.0):
        rotateX=atan2(rotateXa0, rotateXa1)
    return rotateX