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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 process_pc_neighborhood(gene_names, neighbor_limit=1, database_filter=None):
 """Returns a BiopaxProcessor for a PathwayCommons neighborhood query. The neighborhood query finds the neighborhood around a set of source genes. http://www.pathwaycommons.org/pc2/#graph http://www.pathwaycommons.org/pc2/#graph_kind Parameters gene_names : list A list of HGNC gene symbols to search the neighborhood of. Examples: ['BRAF'], ['BRAF', 'MAP2K1'] neighbor_limit : Optional[int] The number of steps to limit the size of the neighborhood around the gene names being queried. Default: 1 database_filter : Optional[list] A list of database identifiers to which the query is restricted. Examples: ['reactome'], ['biogrid', 'pid', 'psp'] If not given, all databases are used in the query. For a full list of databases see http://www.pathwaycommons.org/pc2/datasources Returns ------- bp : BiopaxProcessor A BiopaxProcessor containing the obtained BioPAX model in bp.model. """

    model = pcc.graph_query('neighborhood', gene_names,
                            neighbor_limit=neighbor_limit,
                            database_filter=database_filter)
    if model is not None:
        return process_model(model)