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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 get_ccle_mutations(gene_list, cell_lines, mutation_type=None):
 """Return a dict of mutations in given genes and cell lines from CCLE. This is a specialized call to get_mutations tailored to CCLE cell lines. Parameters gene_list : list[str] A list of HGNC gene symbols to get mutations in cell_lines : list[str] A list of CCLE cell line names to get mutations for. mutation_type : Optional[str] The type of mutation to filter to. mutation_type can be one of: missense, nonsense, frame_shift_ins, frame_shift_del, splice_site Returns ------- mutations : dict The result from cBioPortal as a dict in the format Example: {'LOXIMVI_SKIN': {'BRAF': ['V600E', 'I208V']}, 'SKMEL30_SKIN': {'BRAF': ['D287H', 'E275K']}} """

    mutations = {cl: {g: [] for g in gene_list} for cl in cell_lines}
    for cell_line in cell_lines:
        mutations_cl = get_mutations(ccle_study, gene_list,
                                     mutation_type=mutation_type,
                                     case_id=cell_line)
        for gene, aa_change in zip(mutations_cl['gene_symbol'],
                                   mutations_cl['amino_acid_change']):
            aa_change = str(aa_change)
            mutations[cell_line][gene].append(aa_change)
    return mutations