PEP257: one-liner + paragraph with details:

```python

def _generate_adjacency_matrix(grid_dimensions):
    """Generate an adjacency matrix for nodes of an orthotopic grid.

    grid_dimensions specifies the structure if the grid as a tuple of integers.
    """
```

Also I could not find a good definition of "orthotopic" in a math context. I think the meaning of that word should be explained here.