def canonicalize(self, namespace_targets: Mapping[str, List[str]] = None) -> "<STR_LIT>":
<EOL>if not self.ast:<EOL><INDENT>return self<EOL><DEDENT>if not self.ast.collected_nsarg_norms:<EOL><INDENT>self = self.collect_nsarg_norms()<EOL><DEDENT>self.ast.canonicalize()<EOL>return self<EOL>
Takes an AST and returns a canonicalized BEL statement string.

Args:
    namespace_targets (Mapping[str, List[str]]): override default canonicalization
        settings of BEL.bio API api_url - see {api_url}/status to get default canonicalization settings

Returns:
    BEL: returns self