<put algortithm description here>
Input layer
[raster]Interval between contour lines
[number]<put parameter description here>
Default: 10.0
Attribute name (if not set, no elevation attribute is attached)
[string]Optional.
<put parameter description here>
Default: ELEV
Additional creation parameters
[string]Optional.
<put parameter description here>
Default: (not set)
Output file for contour lines (vector)
[vector]processing.runalg('gdalogr:contour', input_raster, interval, field_name, extra, output_vector)