code: def log(x):
      """evaluates the natural logarithm of an interval"""
      np = import_module("numpy")
      if isinstance(x, (int, float)):
          if x <= 0:
              return interval(-np.inf, np.inf, is_valid=False)
          else:
              return interval(np.log(x))
      elif isinstance(x, interval):
          if not x.is_valid:
              return interval(-np.inf, np.inf, is_valid=x.is_valid)
          elif x.end <= 0:
              return interval(-np.inf, np.inf, is_valid=False)
          elif x.start <= 0:
              return interval(-np.inf, np.inf, is_valid=None)
  
          return interval(np.log(x.start), np.log(x.end))
      else:
          raise NotImplementedError
  
imports: from functools import reduce
  from sympy.plotting.intervalmath import interval
  from sympy.external import import_module
label_desc: Use image node_id 3 for calling a global function with example usage: log(x) and returns: interval, interval, interval, interval, interval, interval