code: def _get_subnet_explicit_route_table(subnet_id, vpc_id, conn=None, region=None, key=None, keyid=None, profile=None):
      '''
      helper function to find subnet explicit route table associations
  
      .. versionadded:: 2016.11.0
      '''
      if not conn:
          conn = _get_conn(region=region, key=key, keyid=keyid, profile=profile)
      if conn:
          vpc_route_tables = conn.get_all_route_tables(filters={'vpc_id': vpc_id})
          for vpc_route_table in vpc_route_tables:
              for rt_association in vpc_route_table.associations:
                  if rt_association.subnet_id == subnet_id and not rt_association.main:
                      return rt_association.id
      return Nonf _get_subnet_explicit_route_table(subnet_id, vpc_id, conn=None, region=None, key=None, keyid=None, profile=None):
      '''
      helper function to find subnet explicit route table associations
  
      .. versionadded:: 2016.11.0
      '''
      if not conn:
          conn = _get_conn(region=region, key=key, keyid=keyid, profile=profile)
      if conn:
          vpc_route_tables = conn.get_all_route_tables(filters={'vpc_id': vpc_id})
          for vpc_route_table in vpc_route_tables:
              for rt_association in vpc_route_table.associations:
                  if rt_association.subnet_id == subnet_id and not rt_association.main:
                      return rt_association.id
      return None
docs: helper function to find subnet explicit route table associations
  
      .. versionadded:: 2016.11.0