<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def complex_to_real(complex_fid):
 """ Standard optimization routines as used in lmfit require real data. This function takes a complex FID and constructs a real version by concatenating the imaginary part to the complex part. The imaginary part is also reversed to keep the maxima at each end of the FID and avoid discontinuities in the center. :param complex_fid: the complex FID to be converted to real. :return: the real FID, which has twice as many points as the input. """

    np = complex_fid.shape[0]
    real_fid = numpy.zeros(np * 2)
    real_fid[:np] = complex_fid.real
    real_fid[np:] = complex_fid.imag[::-1]
    return real_fid