Given a string of Symbolic operators, set each prefactor equal to the

value in coeff. Note that the order in which SymbolicOperators in OpenFermion are printed out is not necessarily the order in which they are iterated over.

operators (FermionOperator) - A linear combination of operators.

coeff (numpy.array(ndim=1,dtype=numpy.complex64)

nothing - mutates coeff in place