def infer_len(node, context=None):
call = arguments.CallSite.from_call(node)<EOL>if call.keyword_arguments:<EOL><INDENT>raise UseInferenceDefault("<STR_LIT>")<EOL><DEDENT>if len(call.positional_arguments) != <NUM_LIT:1>:<EOL><INDENT>raise UseInferenceDefault(<EOL>"<STR_LIT>"<EOL>"<STR_LIT>".format(len=len(call.positional_arguments))<EOL>)<EOL><DEDENT>[argument_node] = call.positional_arguments<EOL>try:<EOL><INDENT>return nodes.Const(helpers.object_len(argument_node, context=context))<EOL><DEDENT>except (AstroidTypeError, InferenceError) as exc:<EOL><INDENT>raise UseInferenceDefault(str(exc)) from exc<EOL><DEDENT>
Infer length calls

    :param nodes.Call node: len call to infer
    :param context.InferenceContext: node context
    :rtype nodes.Const: a Const node with the inferred length, if possible