class_docstr: Provides methods to allow conversion between sheet and matrix
  coordinates.
docstr: Given arbitrary sheet coordinates, return the sheet coordinates
  of the center of the closest unit.
docstr_tok: ["Given","arbitrary","sheet","coordinates",",","return","the","sheet","coordinates","of","the","center","of","the","closest","unit","."]
code: def closest_cell_center(self, x, y):
      """
      Given arbitrary sheet coordinates, return the sheet coordinates
      of the center of the closest unit.
      """
      return self.matrixidx2sheet(*self.sheet2matrixidx(x, y))
  
imports: import numpy
  from .boundingregion import BoundingBox
  from .util import datetime_types
label_desc: Use image node_id 12 for calling the SheetCoordinateSystem obj's underlying member method code with example usage: obj.closest_cell_center(x, y) and returns: self