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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 modeldeclarations(self):
 """Attribute declarations of the model class."""

        lines = Lines()
        lines.add(0, '@cython.final')
        lines.add(0, 'cdef class Model(object):')
        lines.add(1, 'cdef public int idx_sim')
        lines.add(1, 'cdef public Parameters parameters')
        lines.add(1, 'cdef public Sequences sequences')
        if hasattr(self.model, 'numconsts'):
            lines.add(1, 'cdef public NumConsts numconsts')
        if hasattr(self.model, 'numvars'):
            lines.add(1, 'cdef public NumVars numvars')
        return lines