Function require 

pub fn require<T: Element, D: Dimension>(
    a: &Array<T, D>,
    _requirements: &str,
) -> Array<T, D>

Return a contiguous array meeting requirements.

requirements is a string of single-character flags:

• 'C' — C-contiguous
• 'F' — F-contiguous (treated as C in ferray; see asfortranarray)
• 'A' — any contiguous (no-op)
• 'W' — writeable (always true for owned arrays)
• 'O' — owned data (no-op; arrays are always owned)

Analogous to numpy.require. Unknown flags are ignored.