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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 pick_flat_z(data):
 """Generate a 2D array of the quasiparticle weight by only selecting the first particle data"""

    zmes = []
    for i in data['zeta']:
        zmes.append(i[:, 0])
    return np.asarray(zmes)