code: def get_combined_requirements(self, requirements=None):
          
  
          requirements = requirements or self.env.requirements
  
          def iter_lines(fn):
              with open(fn, 'r') as fin:
                  for line in fin.readlines():
                      line = line.strip()
                      if not line or line.startswith('#'):
                          continue
                      yield line
  
          content = []
          if isinstance(requirements, (tuple, list)):
              for f in requirements:
                  f = self.find_template(f)
                  content.extend(list(iter_lines(f)))
          else:
              assert isinstance(requirements, six.string_types)
              f = self.find_template(requirements)
              content.extend(list(iter_lines(f)))
  
          return '\n'.join(content)
docs: Returns all requirements files combined into one string.