add row count for conditional_join

[samukweku]

Brief Description

add a row count for matches from the left dataframe in the right dataframe

Example API

(d2
.conditional_join(
    d1, 
    ('pos', 'segment.start', '>='), 
    ('pos', 'segment.end', '<='),
    ('chr', 'chr', '=='), 
    return_counts=True)
)

[samukweku]

We can possibly extend this idea to aggregate (sum, min,max,...) ... Might be limited to numba at the moment, unless we figure out an efficient way to take advantage of pandas groupby without building a dataframe first 🤔