Get footprints around a set of genomic coordinates

## Arguments

- fragments
IterableFragments object

- ranges
Footprint centers given as GRanges, data.frame, or list. See

`help("genomic-ranges-like")`

for details on format and coordinate systems. Required attributes:`chr`

,`start`

,`end`

: genomic position`strand`

: +/- or TRUE/FALSE for positive or negative strand

"+" strand ranges will footprint around the start coordinate, and "-" strand ranges around the end coordinate.

- zero_based_coords
If true, coordinates start and 0 and the end coordinate is not included in the range. If false, coordinates start at 1 and the end coordinate is included in the range

- cell_groups
Character or factor assigning a group to each cell, in order of

`cellNames(fragments)`

- cell_weights
Numeric vector assigning weight factors (e.g. inverse of total reads) to each cell, in order of

`cellNames(fragments)`

- flank
Number of flanking basepairs to include on either side of the motif

- normalization_width
Number of basepairs at the upstream + downstream extremes to use for calculating enrichment

## Value

`tibble::tibble()`

with columns `group`

, `position`

, and `count`

, `enrichment`