def __init__(self, input_dict=None):
self._p2v = {}<EOL>self._v2p = {}<EOL>if input_dict is not None:<EOL><INDENT>if not isinstance(input_dict, dict):<EOL><INDENT>raise LayoutError("<STR_LIT>")<EOL><DEDENT>self.from_dict(input_dict)<EOL><DEDENT>
construct a Layout from a bijective dictionary, mapping
        virtual qubits to physical qubits