code: protected function _checkVectorSpace(self $b)
      {
          if (!$this->isSameDimension($b)) {
              throw new Exception('The vectors must be of the same dimension');
          }
  
          if (!$this->isSameVectorSpace($b)) {
              throw new Exception('The vectors\' components must have the same keys');
          }
      }
docs: Checks that the vector spaces of the two vectors are the same.
  
  The vectors must be of the same dimension and have the same keys in their
  components.
  
  @internal
  @param self $b The vector to check against.
  @return void
  @throws Exception if the vectors are not of the same dimension.
  @throws Exception if the vectors' components down have the same keys.