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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 calc_sasa(dssp_df):
 """ Calculation of SASA utilizing the DSSP program. DSSP must be installed for biopython to properly call it. Install using apt-get on Ubuntu or from: http://swift.cmbi.ru.nl/gv/dssp/ Input: PDB or CIF structure file Output: SASA (integer) of structure """


    infodict = {'ssb_sasa': dssp_df.exposure_asa.sum(),
                'ssb_mean_rel_exposed': dssp_df.exposure_rsa.mean(),
                'ssb_size': len(dssp_df)}

    return infodict