code: def get_single(decl_matcher, decls, recursive=True):
          
          answer = matcher.find(decl_matcher, decls, recursive)
          if len(answer) == 1:
              return answer[0]
          elif not answer:
              raise runtime_errors.declaration_not_found_t(decl_matcher)
          else:
              raise runtime_errors.multiple_declarations_found_t(decl_matcher)
docs: Returns a reference to declaration, that match `decl_matcher` defined
          criteria.
  
          If a unique declaration could not be found, an appropriate exception
          will be raised.
  
          :param decl_matcher: Python callable object, that takes one argument -
              reference to a declaration
          :param decls: the search scope, :class:declaration_t object or
              :class:declaration_t objects list t
          :param recursive: boolean, if True, the method will run `decl_matcher`
              on the internal declarations too