old_contents: import os
  
  from .checker import CheckerBase
  from .report import EnvReporter
  
  class EnvironmentChecker():
      def __init__(self, outpath, *checks):
          self.checks = []
          if checks:
              self.checks = list(checks)
          self.problems = []
          self.reporter = EnvReporter(self, out=outpath)
  
      def register(self, *checks):
          """Add checks to this checker"""
          for chk in checks:
              if hasattr(chk, '__iter__'):
                  self.checks.extend(chk)
              else:
                  self.checks.append(chk)
  
      def check_all(self):
          for check in self.checks:
              rv = check()
              if rv:
                  self.problems.append(rv)
  
          self.reporter.write_report()
  
new_contents: """Checker object for verifying environment variables"""
  
  from .checker import CheckerBase
  from .report import EnvReporter
  
  class EnvironmentChecker():
      def __init__(self, outpath, *checks):
          self.checks = []
          if checks:
              self.checks = list(checks)
          self.problems = []
          self.reporter = EnvReporter(self, out=outpath)
  
      def register(self, *checks):
          """Add checks to this checker"""
          for chk in checks:
              if hasattr(chk, '__iter__'):
                  self.checks.extend(chk)
              else:
                  self.checks.append(chk)
  
      def check_all(self):
          for check in self.checks:
              rv = check()
              if rv:
                  self.problems.append(rv)
  
          self.reporter.write_report()
  
subject: Add module docstring