MethodError: no method matching imagesc(::Array{Float64,2}, ::Nothing, ::Nothing, ::Nothing)

New to Julia
3

This is my error:
Error During Test at /home/pranjaliraturi/EchogramImages.jl/test/runtests.jl:6
Got exception outside of a @test
MethodError: no method matching imagesc(::Array{Float64,2}, ::Nothing, ::Nothing, ::Nothing)
Closest candidates are:
imagesc(::Any; vmin, vmax, cmap, size) at /home/pranjaliraturi/.julia/packages/EchogramImages/rVj6X/src/EchogramImages.jl:38

The following is my code:

using EchogramImages
using Test
using EchogramColorSchemes
using ColorSchemes

a = rand(100,100)
img = imagesc(a, nothing, nothing, nothing)
m,n = size(img)
@test m == 480
@test n == 640
@test cmap == cmap.colors
@test typeof(vmin) == AbstractFloat
@test typeof(vmax) == AbstractFloat
@test vmin <= @. img <= vmax
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This is the function that was already created:

using Images
using MappedArrays
using IndirectArrays
using EchogramColorSchemes
using ColorSchemes

export imagesc, mat2gray, equalizedbins, quantize

"""
imagesc(A; vmin = nothing, vmax = nothing, cmap= nothing, size=(480,640))

A is any numeric array

cmap can be a list of Colors or can come from EchogramColorSchemes.jl,
ColorSchemes.jl or PerceptualColourMaps.jl. The default  `nothing`
currently means use EK80 colours.

Set size = nothing for full resolution.

vmin and vmax are minimum and maximum values.

"""
function imagesc(A;
vmin = nothing,
vmax = nothing,
cmap= nothing,
size=(480,640))

if cmap == nothing
    cmap = addwhite(EK80)
end

if isa(cmap,ColorScheme)
    cmap = cmap.colors
end

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.
.
.
end

I’m assuming it’s because I’m passing incompatible types in the function imagesc. However I assumed the function’s prototype from the function logic and my mentor was generous enough to give me a general idea of what was going on. Please let me know what’s up and I’ll try to fix it. All the help is appreciated!!